Troubleshooting Alternator and Charging System Problems

Updated on January 19, 2019
Dan Ferrell profile image

Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology.

The alternator is at the heart of the charging system of your vehicle.
The alternator is at the heart of the charging system of your vehicle. | Source

Alternator problems and charging system problems can affect your vehicle in different ways. You may notice:

  • your ALT or CHARGE indicator light comes on,
  • your engine is hard to start and cranks slowly, or doesn't crank,
  • your battery demands lots of water,
  • your alternator makes noises,
  • or your headlights suddenly go dim.

These and other problems may be caused by a fault in the charging system.

Before you start replacing components with the hope of fixing the problem, you need to determine which component or components are causing you trouble. Often, it is possible to diagnose and solve the problem on your own using a few simple tests and tools.

The sooner you find out what is causing trouble, the better. You'll prevent a faulty component from ruining other parts in the system, which would make your repair more expensive.

This convenient troubleshooting guide will help you find out what you need to know, using a few simple checks you can do at home using a test light or digital multimeter (DMM) and possibly a few other common tools.

It is a good idea to have on hand the vehicle repair manual (or a good aftermarket manual) for your particular car make and model. It will help you identify wires, specific components, and possibly suggest some specific tests recommended by your manufacturer.

If you want to test the condition of the system as a diagnostic starting point, do the tests described in the following section, "General Charging System Check."

However, if you need help for a specific problem with your charging system—for example, an over-charge or under-charge condition, discharging battery, or noisy system—then skip over to the "Charging System Problems and Potential Causes" section.

Index
I. Common Symptoms of a Bad Alternator or Charging System
II. General Charging System Checks
III. Charging System Problems and Potential Causes
IV. Troubleshooting for Unusual Voltage System Drops
The battery indicator should turn off when your engine is running.
The battery indicator should turn off when your engine is running. | Source

I. Common Symptoms of a Bad Alternator or Charging System

Indicator Light On

Usually, the first sign that your charging system is in trouble is a "battery," "ALT," or "CHARGE" warning light illuminating on your instrument panel while driving. It means that for some reason, the alternator has stopped charging the battery and your car is running on battery power. If the light illuminates only intermittently, it usually indicates worn-out or bad carbon brushes in the alternator. But remember that the light doesn't always mean there is a bad part; the light may be triggered by a sensor giving a wrong message.

Engine Cranks Slowly or Not at All

When the battery is undercharged, the engine cranks slowly or doesn't crank at all. Go over the next section on "General Charging System Checks," and, if necessary, check the section "IV. Troubleshooting for Unusual Charging System Voltage Drops." further down in this article.

Battery Overheating and Using Too Much Water

An overcharged battery causes the battery to overheat. You find yourself adding water to the battery frequently. If the problem is not taken care of on time, it can ruin your battery. Besides going through the next section, make sure to check section IV below on "Troubleshooting for Unusual Charging System Voltage Drops"

Noises Under the Hood

Squealing, buzzing or grinding noises coming from the engine may be caused by bad alternator components, a loose or worn-out serpentine belt, or a faulty belt tensioner. See the "Checking for Alternator Noises" subsection further down in this article.

Dimming Lights

If you notice the headlights, instrument panel, or interior lights dimming, either your battery has a low charge, or there's one or more faulty diodes inside the alternator. Check your battery and see the "Alternator AC Voltage Leak Check" subsection further down in this article.

Check the drive belt for adjustment and tensioner for proper operation.
Check the drive belt for adjustment and tensioner for proper operation. | Source

II. Six Tests for the Charging System in General

These series of charging system checks help diagnose the general condition of your charging system. They can help you confirm that you actually have a problem in your charging system and locate the source of the problem.

1. Make a Visual Inspection of the System

With the engine off, pop the hood open and visually inspect the different components of the charging system. Look for a worn out or loose drive belt, alternator connection problems, loose alternator mounting bolts, and corrosion and dirt around the battery case and cables.

When inspecting the drive belt, check for adjustment. If necessary, adjust the belt with the help of your car owner's manual or repair manual. Inspect the belt for signs of cracks, cuts, shiny spots, deterioration or other signs of wear or damage. Change the belt and belt tensioner at the manufacturer's recommended interval.

2. Check for Wiring Problems

Inspect the wires and connections at the back of the alternator, at the remote voltage regulator (if applicable), and at the battery. Look for corrosion at the connectors, damaged wires, and burned and missing insulation that might suggest an electrical short.

3. Do This If the Indicator Light Stays On, or Goes On and Off

Follow the next steps:

  • Start the engine and apply the emergency brakes. Set the transmission to Neutral (manual) or Park (automatic).
  • Connect a voltmeter across the battery terminals.
  • While watching the voltmeter display, start wiggling wires at the back of the alternator, the battery, and the remote voltage regulator (if there is one).
  • If the voltage reading on the meter display goes up while wiggling one of the wires, you've found a bad electrical wire or connection.

Instead of using a voltmeter, you can have an assistant watch the indicator light on the instrument panel to see if it turns off as you wiggle various wires and connectors. Once the light turns off, you've found the problem connector or wire.

4. Check for Alternator Noises

Bad alternator bearings, rectifiers, rotor shaft, stator winding, slip rings, brushes and other parts inside the alternator with mechanical or electrical problems can become noisy.

Here's a test you can do: Use a length of vacuum hose to listen for alternator noises. The hose will amplify the noise if it's coming from the alternator. But be very careful around moving parts while you do this test.

  • Start the engine.
  • Place one end of the hose against your ear and move the other end around different points of the alternator body.
  • Listen for whining noises (this can indicate a bad diode or an over-charging condition), grinding (bad bearing), squealing, or other abnormal noise. If necessary, have your alternator checked.

5. Check for Under-Charging and Over-Charging

The next three tests are best done using a load tester, but you still can use your digital voltmeter. You do this by measuring system voltage while loading the system.

5a. First, measure battery base voltage to make sure you have a fully charged battery.

  • Turn on the high beams for 10 seconds and then turn them off.
  • Wait for two minutes
  • Measure battery voltage across the battery posts with your DMM. You should get between 12.4 and 12.6V. This means your battery is fully charged. If you get a reading below 12.4V, charge the battery before continuing.
5b. Measure the Charging System's No-Load Voltage
  • Ask an assistant to start the engine and hold engine speed at about 1500 RPM.
  • Measure voltage across the battery with your DMM. You should get 0.5 to 2 volts higher than base voltage. If you are getting more than 2 volts above base voltage, most likely your alternator is over-charging the battery or the battery is faulty. Other potential problems are a faulty voltage regulator or a problem in the charging system wiring. As part of your wiring checks, see the section "Troubleshooting for Unusual Charging System Voltage Drops" below.

5c. Measure charging system load voltage with a high-current-condition system measurement.

  • Ask an assistant to start the engine and hold engine speed at about 2000 RPM. Turn on all electrical accessories like A/C, blower motor, headlights, defroster, wipers. But don't turn on the heated windshield if your vehicle has one; alternator voltage may increase to over 100V and this can be unsafe.
  • Take a voltage reading across the battery posts. Your reading should be at least 0.5 volts above base voltage for your system to keep up with electrical system demands. Otherwise, the charging system can't meet the demand and charge your battery. This fault could point to a faulty alternator or voltage regulator. Check the section "Troubleshooting for Unusual Charging System Voltage Drops" below to check for wiring problems that can lead to this condition.
  • NOTE: These measurements correspond to an ambient temperature of about 70º F. The charging voltage will increase as temperature drops, and charging voltage will decrease as temperature goes up. So keep this in mind when making your measurements.

6. Check for Alternator AC Voltage Leak

Alternators use diodes to rectify alternating current produced by the alternator into direct current. When one or more diodes go bad, the alternator can cause all kinds of problems. AC voltage leak can cause your lights to dim and drain power from your battery, for example. Usually, you can detect this leak by measuring AC voltage across the battery posts using a digital multimeter.

  • Start and let the engine idle.
  • Set the parking brake and your transmission to Park (automatic) or Neutral (manual).
  • Set your meter to a low AC voltage range and take your measurement.
  • If you detect even a small amount of AC voltage, replace the alternator.

Once you've determined the condition of the system, you can go over the next section to zero in on the potential problem(s) that may be causing the condition of the charging system.

A single bad battery cell can prevent your charging system from working properly.
A single bad battery cell can prevent your charging system from working properly. | Source

III. Charging System Problems and Potential Causes

To speed up your diagnosis and repair, look up the system condition that most resembles your problem and go over the potential causes described under that condition. Some checks or tests may be suggested as appropriate.

1. If the Battery Seems to Stay Undercharged

You have already charged your battery a couple of times and you just found out the battery is undercharged again. Before you blame your battery, or the alternator, here are some preliminary checks you may want to do.

a) Check the drive belt or serpentine belt, especially if you haven't replaced it in the last five years. Make sure the belt has the proper tension. Look for signs of wear or damage like cuts, shiny spots, missing chunks. Today serpentine belts don't show signs of wear, even if they need to be replaced. Use a belt wear indicator or check your maintenance schedule for the replacement interval suggested by your car manufacturer. You may find the schedule in your car owner's manual or your repair manual.

b) Along with the drive belt, check the belt tensioner as well. Make sure it turns freely and is noise-free. Car manufacturers recommend replacing the tensioner at the same time you replace the drive belt.

c) Make sure your battery connections are tight and clean. However, just because the terminals look clean, it doesn't mean they are tight and in good condition. Look for damage to the cable and the terminal itself that may prevent proper electrical current flow.

d) Check your battery yourself, or take it to your local auto parts store. Many of these stores will test your battery for free.

e) There's a parasitic battery drain stealing power from your battery.

  • A quick test is to connect a test light in series between the positive battery cable and the positive battery post. If the test light comes on, there is an electrical drain in one of the systems.
  • First, unplug the alternator electrical connector. If the test light goes out, the alternator is causing the drain. If not, locate the parasitic drain.

f) Don't overlook the starter motor: a failing starter motor may draw excessive current during operation, draining battery power. If necessary, have your starter motor or starting system tested.

2. If the System Seems to Be Over-Charging

Besides test results, another potential sign that your battery is being overcharged is that your battery terminals keep accumulating corrosion.

Here are some checks you want to do:

  • Make sure that all the connections to the alternator, remote voltage regulator (if applicable) and battery are clean, tight and in good condition.
  • Check your battery or have it tested at your local auto parts store. A bad battery cell can cause the alternator to over-charge the good battery cells.
  • Check for a bad alternator voltage regulator and circuit. Consult your vehicle repair manual, if necessary.
  • Make sure you have good ground connections at the alternator (alternator case) and voltage regulator, especially if your vehicle uses a remote voltage regulator. Grounds should be free of rust, and the alternator and remote voltage regulator mounting bolts should be clean and tight.
  • Check the alternator rectifier or have your alternator checked at the auto parts store.
  • Also, conduct the tests described in the Troubleshooting for Unusual Charging System Voltage Drops below.

3. If the Alternator Is Not Charging the Battery

When your tests point to an under-charge or no-charging condition:

  • Make sure the drive belt is not loose or worn out.
  • If necessary, borrow a good battery just to operate the engine and confirm that your drive belt and belt tensioner are operating properly.
  • Manually check the belt tensioner for proper operation. Make sure the tensioner pulley turns freely and without noise. Check it for damage.
  • Manually turn the alternator pulley and make sure it turns without a problem. If one of the bearings has seized, it won't allow the alternator to turn freely.
  • Check that the connections at the battery, alternator, and remote voltage regulator are clean and tight.
  • Check for a blown fuse or fusible link. Consult your vehicle repair manual, if necessary, to locate the alternator fuse or fusible link.
  • Do the tests described in the section "Troubleshooting for Unusual Charging System Voltage Drops" below.

4. If the Engine Makes Noises

Noise can be a sign of alternator problems when it comes from the charging system. The next checkpoints will help you isolate the source of the noise.

  • Check the drive belt or serpentine belt. Look for signs of wear or damage like cuts, shiny spots or missing chunks under the belt. A worn out belt can squeal during operation.
  • Also, check the belt tensioner for proper operation and damage. It should rotate freely.
  • Make sure the alternator is properly mounted. Loose mounting bolts can cause the alternator drive belt and drive pulley to become misaligned and noisy.
  • Check the alternator for noises. See the General Charging System Checks section for a simple procedure for this.

5. If Lights Dim During Engine Operation

Most alternators use diodes inside a rectifier to turn Alternating Current (AC) into Direct Current (DC) for use by the system. When one or more diodes go bad, AC can leak into the electrical system. Sometimes you can notice this when the headlights, instrument panel lights, and other interior lights dim during engine operation. To test your alternator for AC current leaks, see the Alternator AC Voltage Leak Check subsection in the previous section.

Measure system voltage and drop voltages using a digital multimeter.
Measure system voltage and drop voltages using a digital multimeter. | Source

IV. Troubleshooting for Unusual Charging System Voltage Drops

A charging system voltage drop check can help you locate the source of an under-charge or over-charge condition due to problems in the wiring or connections between the battery and alternator.

1. Start the engine and let it idle. Apply the parking brake and set the transmission to Neutral (manual transmission) or Park (automatic transmission).

2. Turn on the high beams, AC, wipers, and other accessories to provide a system load. Have an assistant raise engine speed to about 1500 RPM. But if your vehicle is equipped with a heated windshield, don't turn it on; this can make alternator voltage go over 100 V. Since you'll be working around alternator connections, this could be dangerous.

3. With your voltmeter test leads, touch the positive battery post and the B+ terminal connector at the back of the alternator.

4. Check your meter display. You should get around 0.2V or less of voltage drop. Getting 0.3V or more can lead to an under-charge condition. Check the connections in that part of the circuit for a loose wire, corrosion at the connectors or wiring damage that may prevent proper current flow between the battery and alternator. Also, check the electrical connections at the back of the alternator and at the voltage regulator.

5. Now repeat the test, but this time, connect your meter leads between the battery negative post and the alternator case.

6. Check your meter display. Again, you should get a voltage reading around 0.05V. If you get 0.1V or more, there's something wrong. This can lead to an over-charging condition. Checking that part of the circuit, make sure the battery ground connection is good, clean and tight. Add a temporary ground connection from the battery to the chassis. If this removes the high voltage drop, check the engine to body grounds connections. They should be clean, tight and in good condition.

Watch the next video for a visual reference on voltage drop checks.

Alternator problems are not uncommon after a few years of operation. A typical alternator may last anywhere from 8 to 12 years. So don't be surprised to find your alternator going bad or the system developing problems after a few years of trouble-free operation, even if you have maintained your car well.

The key point here is to do the proper diagnostic as soon as possible because a bad alternator can ruin an otherwise good battery, and other components as well, depending on the fault.

Once you determine that your alternator is bad, you have several options. You can replace it with an original one from your dealer, an aftermarket replacement, or a rebuilt unit. Aftermarket alternators are a good option and less expensive, and many of them are just as good as their OEM counterparts. And rebuilt alternators are not as bad either. So consider your options.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

  • I have a 2005 Ford Taurus one day it wouldn’t start. It finally started and flashing lights to check the brake system in the charging system, but then it wouldn’t start once it was jumped. It kept stalling, so we had it checked at an auto parts store. They agreed alternator replaced the alternator and it is still doing the same thing do you have any idea what else could be wrong?

    Check all the grounds -- battery to body and body to engine. They should be clean and tight. Bad grounds can eventually, damage the alternator. Test for voltage drop on the grounds, battery and charging system.

  • I have a 2011 Mazda 3, 2.5. The battery light turned on when I was driving at 120 km/h and would turn off if I slowed down. The light now starts at 90 km/h and will turn off if I slow down (maybe rpm related, not sure). Battery, alternator and start engine were tested at the dealership but seem to be OK. The battery seems to slowly drain within a few weeks as the speed decreases for the battery light to turn on. What could it be?

    This may be an alternator issue with worn brushes, slowly losing the ability to charge the battery. A common test is to replicate engine rpm at which the light comes on. Watch the engine rpm when the battery light comes on. At home, with the transmission in Neutral or Park, increase engine speed to the same rpm and see if the light comes on. If it does, the alternator needs new brushes.

  • I have a 2001 Toyota Solara with 158,000 miles. I've gone through 5 alternators in about 6 yrs. Even the Toyota oem. Two reliable mechanics can’t figure it out. I’m taking it to a shop that specializes in electrical problems. Do you have any ideas?

    Knowing how the previous alternators failed can give a clue about the type of issue you are dealing with (electrical, mechanical). Usually when alternators failed prematurely is because of a bad battery (electrical), voltage regulator issues, high electric loads (e.g. running AC fan at high) or a drive belt that is putting unusual stress on the alternator pulley (mechanical)(make sure the belt is not too tight). Alternator quality can be another factor of course.

    Check for signs of fluid leakage around the alternator that might affect the stator or rotor or both.

  • I have a good alternator, but my battery runs down. It passed tests performed at two auto parts stores. When this problem occurred, I was able to get home by starting the vehicle (2000 GMC Yukon, 5.3L) by disconnecting the battery. Voltage when up close to 14 according to the gauge. When I reconnected the batter at home, it was still dead. Got a new battery and have the same problem with battery drain. Do you have any ideas?

    If you have some power amplifier, or some other power accessories, this could be running down the battery if the alternator can’t keep up with the demand. Other than that, you may want to have the alternator checked in a shop, and see where the charge is going while the engine is running.

    You can check for a parasitic drain that you may not be aware of. This post can help you:

    https://axleaddict.com/auto-repair/car-batterydrai...

  • I installed a new 105-amp alternator in my 1982 Chevrolet C10. When I start the engine, it indicates 14.6 volts on the voltmeter connected to the battery. When I start the AC fan and the AC compressor, the voltage increases to 15.8 volts. After a while, the alternator stops charging; I think it might be defective. I changed two alternators, but I still have the same problem. What do you think?

    Check the voltage regulator and the battery. An auto parts store may check the battery for you. Also, may sure the circuit connections for the charging system are clean and tight and check the engine body grounds.

Comments

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    • profile image

      Jim 

      2 weeks ago

      Hello there Dan!

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      3 weeks ago

      A bad fussible link between the starter solenoid and alternator sometimes cause this problem. Check all the fuses and check for trouble codes. If you don't have a scanner get a free scan from your local auto parts store. Sometimes a sensor may cause this problem as well.

    • profile image

      Lisa Williams 

      3 weeks ago

      I have an 07 Hyundai Sonata I’ve had the alternator replace an the servertine belt my battery light an brake light an air bag light is on plus my ac don’t work it was working all before

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      5 weeks ago

      Check the charging circuit voltage drop. There may be too much resistance, causing the alternator's temperature to rise:

      https://axleaddict.com/auto-repair/Charging-System...

      Hope this helps.

    • profile image

      Thomas messner 

      5 weeks ago

      My battery goes dead after 2days , I have noticed that my dash charge cluster goes up & down only wen I use signal or wipers is there a bad cluster or wiring, I hav changed alternator 2 times it gets hot to touch wat is problem?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      6 weeks ago

      it seems the probelm is either in the charging circuit or the engine grounds. Check the wires for the alternator and the circuit. These other two posts may help:

      https://axleaddict.com/auto-repair/Automotive-Volt...

      https://axleaddict.com/auto-repair/Charging-System...

    • profile image

      Chris Ramirez98 

      6 weeks ago

      hello,I have a 99 Lexus ES300 and I've been having major electrical problems with her. started to show the first symptom of not starting (would need a jump about once a week or two) next the car would struggle to start, then the lights in the cab and headlights were going dim, next they were vigorously pulsing and get faster with the speed of the car. we have replaced the battery, alternator, starter, positive cable leading to starter (it was visually very corroded) and made sure all connections were secure. the car starts to loose power after driving and we have concluded so far that the car is running off the battery solely Another symptom is the dash lights and center console loose power first as a warning the the car is about to die. the RPM needle goes wacky and then the car is struggling to move forward. if you cut the lights and radio and A/C in this situation the car gets the last amount of juice and rides good again enough to get to a safe place. We don't know what it is and have begun looking at the grounding cables and still flying blind trying to solve the issue. help is very much needed to anyone who has expertise. please help me. (after replacing the alternator the battery light has been consistently on even with the change of the other parts.

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      8 weeks ago

      There could be a problem in the charging system. If the computer regulates voltage output in the system, check there too. Try checking for trouble codes, even if the check engine light is not on. There could be a pending code.

    • profile image

      Claburn 

      8 weeks ago

      Hi Dan got a 2017 pathfinder battery light cane on car stop moving . Had celeration in Park and neutral but not in drive change the alternator all was fine for a week and the sane problem again any answers .

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      2 months ago

      There could be a loose wire in the circuit. If you need to test the alternator, this other post may help you:

      https://axleaddict.com/auto-repair/Alternator-Prob...

    • profile image

      Stone Emmanuel 

      2 months ago

      Please i have a 2003 golf 4 when ever i start the engine will start normally, i expect the Alternator and the fan to start working but i notice i have to raise my car before the Alternator will start working even when the engine is hot ...i just have to raise the car b4 the alternator will start working...what can i do

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      2 months ago

      Probably the nut holding the stud to the rectifier is loose. You can try taking it apart and tighten the bolt. If the insulator is damaged, you'll probably need to replace the alternator, unless you can install a new battery stud kit.

    • profile image

      Zerina Wilson 

      2 months ago

      I cannot get the bolt to connect battery to alternator tight. Is there a way to tighten it do I take alternator apart and replace the Standard Ignition Alternator Terminal?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      2 months ago

      Check the fuses and the electrical connectors. A wire might come loose or a fuse blown when they replaced the alternator. Hope this helps.

    • profile image

      Jannin 

      2 months ago

      I had my alternator changed but now my lights will not come on nor will my alarm work what can be done to fix it?

    • profile image

      Vaderdude 

      3 months ago

      Nice job here.

      I would love other people's two cents on these. For the sake of argument, presuming there is no parallel causes.

      1- Is it possible to cause a short if the battery is hooked up back with the alternator removed? In this case presume that all connectors are protected and not exposed, not dirty, rusty, oxidized, compromised, etc ....and in excellent conditions.

      2- Spraying electrical connectors with proper electronic cleaner, could it potentially cause troubles, assuming that connector were not damaged by handling....

      3- Can oil spill on connector potentially cause a short?

      Thank you for sharing your opinion and experience.

    • profile image

      Dawit Berhe 

      5 months ago

      Keep it up

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      5 months ago

      Check the charging system circuit. Sometimes the fusible link, if the circuit has one, is the faulty part.

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      5 months ago

      Check the charging circuit. If it is Okay, the circuit to the warning light is shorted.

    • profile image

      Malcolm Jenkins 

      5 months ago

      Both my battery and alternator are good but i still need jumps

    • profile image

      Vijanda 

      5 months ago

      Hi my alternator was repaired but if i pulled out one battery plug the car go off but the battery light is off.

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      6 months ago

      There's a special circuit for the battery indicator on the dashboard. Something is feeding power to the circuit, possibly a bad ground. You might want to ake a look at the wiring diagram at the repair manual for your model. If you don't have the manual, check the reference section of your local library. Hope this helps.

    • profile image

      Justin 

      6 months ago

      My 97 4Runner has had a battery light on for 2 years now. Hasn’t effected driveability. Installed a voltemeter to read battery output and is always 12.4-12.6 off and 13.6-14.1 on. Question is what would be the cause of my light if there’s not an over charge or under charge? Like I said been on 2 years along with abs light. What’s the cultiprit

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      7 months ago

      This usually occurs when the ignition coil develops a short that causes high current draw, overheating the module and eventually burning it. Look for white residue under the cap (if module is located inside). You might want to check the coil or have it checked. This post may help:

      https://hubpages.com/autos/How-to-Test-an-Ignition...

      When replacing the module, make sure to apply the grease to the backing plate of the module, and if possible, use only the OEM product. Hope this helps.

    • profile image

      Adam 

      7 months ago

      My dad's Honda ballad 150 1995 keep on burning the modules one after the other it doesn't even start

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      7 months ago

      It is wearing out the belt and putting a stress on other pulleys and engine. If you plan in fixing the AC at a later time but want to use the car, you can try finding a shorter serpentine belt or install an AC compressor bypass pulley. Just search online for your specific model. Hope this helps.

    • profile image

      Orlando 

      7 months ago

      Having trouble finding exact issue on my 05 ford escape. Trying to avoid spending too much for a part that wasnt the problem. A question, if a/c compressor pulley is not free spinning on its own but belt is sliding right past it as intended would that put strain on any other parts associated, with desired effect. Like other pulleys or not maintaining a charge on battery?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      8 months ago

    • profile image

      jason.jjcm@gmail.com 

      8 months ago

      1995 Honda Accord engine won't start

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      9 months ago

      Most likely there’s a problem in the charging circuit, since you have a charging problem. If you have the wiring diagram for the charging circuit (vehicle repair manual), locate the wire for the warning light. Usually this is marked IND or WL on the back of your alternator, but double check your diagram. Ground this wire and turn the ignition to On. If the warning light comes on, there’s a problem in the circuit; otherwise, the bulb is blown. But I believe, even if the bulb doesn’t come on, there is a problem in this part of the circuit causing you trouble. Hope this helps.

    • profile image

      Bolara 

      9 months ago from USA

      Hello . I have a 2009 Toyota Avalon XLS

      One day all lights flashed and shortly they went off and the car stopped. I was told it’s the alternator and it was replaced and problem was fixed , that was a year ago . Yesterday I had the same problem and Firestone said it’s the alternator. The problem started a week ago when battery light flashed for a minute then disappear and come back days later and disappeared until yesterday when the car stopped. I have doubts about the alternator as the battery light is not on before engine start or after . It’s simply not there yet the alternator is not charging . I disconnected the alternator cables and started the engine to see if the light will come on with the alternator disconnected, but no , it didn’t come on at all . Now I am confused. I don’t want to pay another $ 600 to replace the alternator. I need to understand why the alight is not on when the alternator is not charging? What to do . Everything around the alternator looks clean and functional. Any help ? Thank you

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      9 months ago

      You might want to try checking the circuit voltage drop, there could be a bad wire you can’t easily see just by looking at it. This post can give you an idea about checking for voltage drop:

      https://axleaddict.com/auto-repair/Automotive-Volt...

    • profile image

      Malik 

      9 months ago

      Question. I have a 2000 lexus gs300 the alternator is reading bad voltage regulator. Ive changed the alternator 3 times. when i get them bench tested they pass but when i put it in the car it fails. Ive checked my wires, cleaned my ground connectors, and checked the fuses. PLEASE HELP?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      9 months ago

      You may want to do a voltage drop test on the charging circuit (between battery positive and battery connection on the alternator; and battery negative and alternator ground).

      This post gives you an idea about the test:

      https://axleaddict.com/auto-repair/Automotive-Volt...

    • profile image

      Adrew Jackson 

      9 months ago

      I have a 1999 ford f150 and after i replaced the battery the truck was still losing power. So i replaced the alternator. Now im losing power but nowhere near as fast, but its still happening.. what could the problem be

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      10 months ago

      Have the alternator checked. There could be a problem with the voltage regulator.

    • Steve Swaddling profile image

      Steve Swaddling 

      10 months ago

      How do I find a short for an overcharging alternator

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      11 months ago

      You need the wiring diagram for your particular make and model. Check where those wires connect to and see if yours is supposed to have a reading.

    • profile image

      Timothy Mason 

      11 months ago

      I have a 2012 kia sorento. pulled the alternator had it check on a bench test and it passed. The power wire, fuseable links, fuses all with alternator still out of the car. everything came back with the normal .2 .3 ohms reading. I found an aritcle that said to connect the black wire of my multimeter to the ground on the batter and positive check the 4 insertes of the plug that connects into the alternator. The video showed all 4 had a reading mine only showed one. So i did the opposit placed the positive on the batter and negavitve checked my plug and the opposite one gave a reading but again not all 4. Is it supposed to have a reading in all 4 plug ends? And if not what else can i do to diagnose where my short is?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      11 months ago

      There could be a problem in the charging system. The noise may come from a pulley, making the belt loose. This other post might help:

      https://axleaddict.com/auto-repair/Serpentine-Belt...

    • profile image

      Loveis 

      11 months ago

      Hi, Thank you in advance! I have a 2001 Infiniti g20 and It starts but wont stay running and the battery is draining after I charged it at autozone. I just replaced the alternator and still wont stay running. I do hear a loose pulley or something near the alternator, but don't know exactly where yet. What else can I do to get the car running again. It will run, just battery died quickly and abs and battery light flashes on and off. Can you give me any pointers? Thank you!

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      12 months ago

      It's possible you have a loose wire or connection. Have somebody watch the warning light while wiggling wires and connections and see if the light comes on. Also, you may want to try doing a voltage drop on the charging circuit. This post will give you an idea about how to go about it,

      https://axleaddict.com/auto-repair/Automotive-Volt...

    • profile image

      Noah Smith 

      12 months ago

      I just replaced my alternator on my 06 mustang gt. The diodes were bad and was causing a check engine light ive never had the battery light come on. But it came on right after i changed the alternator. It comes on for a few seconds then turns off for a while. Ive already double checked my work. And tested the battery with the car running and the battery stays around 13.7 volts.

      I dont want to drive my car until i figure it out. I Dont want to get stranded.

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      13 months ago

      Sorry, I'm not familiar with the system, but probably this might help you. Good luck

      https://cpower.com/PDF/InfoSheets/39.pdf

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      13 months ago

      Hi Mayo,

      Go over section IV in the post. This might help with the problem.

      Good luck.

    • profile image

      LB Mayo 

      13 months ago

      1993 F250 4x4 7.5 gas engine. I am having charging problems any time I run ac or headlights. New alternator, new alt. Belt, cleaned batt.post,cables and all wires on fender mounted starter solenoid. Had battery checked twice. What else could it be?

    • profile image

      RJ SAYMO 

      13 months ago

      HELLO !

      MAY I ASK A QUESTION . ABOUT GENERATOR SET .

      WHEN THE GENSET RUN WITHOUT LOAD THERE IS AN ALARM HIGH VOLTAGE BATTERY 30.2V . WHAT IS THE PROBLEM OF THIS SITUATION ..

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      13 months ago

      Hi John,

      It seems as if there's something drawing too much power. Possibly an amp? But why the headlight go dim with radio off, but with headlamp and AC on (and radio still off?) the charge maintains. I'd start by checking the alternator and battery fist. Make sure they are good.

    • profile image

      John 

      13 months ago

      I have a Hyundai i10 year 2010, my car have a 13.3V charge (idle) when I switch on headlamp and AC at the same times, radio will on and off for 1-2 seconds (idle), headlight will go dim when radio is off. When RPM2000, charge will increase to 13.6V.

      If I only switch on headlamp / AC, charge will maintain 13.8-14.2V.

      Is it my car's alternator problem?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      13 months ago

      remove the belt and try spinning the AC pulley by hand. It should spin freely - if there's noise or the pulley feels rough,noisy, you'll need to replace it.

    • profile image

      Douglas Anayabere 

      13 months ago

      My compressor belt is dragging when i switch the aircondition on. What is the problem?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      14 months ago

      Hi Ron,

      Check the voltage regulator.

      Hope this helps.

    • profile image

      Ron 

      14 months ago

      Put new battery and altinator on 2001 f150 and its still over chargeing is it the pcm?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      14 months ago

      Hi Aaron

      Check the battery cables for corrosion and make sure they are tight. Also check the connecitons to the alternator and wires. Also, make sure the alternator belt is not loose or worn. If all that turns out okay, check the battery. An auto parts store will check the battery for you, if necessary.

      Hope this helps

    • profile image

      Aaron 

      14 months ago

      My corolla 2e battery light remain even when the alternator is charging. What could be the fault?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      15 months ago

      Hi Keith,

      I don't have the diagram with me but probably this pic might help. I believe is the same model.

      https://cdn4.pelicanparts.com/techarticles/BMW_200...

      Otherwise you can check the repair manual in your local library.

      Good luck

    • profile image

      Keith Irons 

      15 months ago

      Need to know what does the spade connecter go to for 1982 bmw 320i on the alternater

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      15 months ago

      Hi Enos,

      They should test the circuit (wires and connections), ground (engine) connections and make sure the correct output voltage is coming out of the alternator and getting to the battery.

      Good luck

    • profile image

      Enos Kaufman 

      15 months ago

      alternator was changed even the one changed out tested fine Napa still flatlined im lost now

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      15 months ago

      You might get occasionally over 16V from the alternator. Have your battery checked at a local auto parts store.

    • profile image

      Don 

      15 months ago

      How about of light is on, but have 24.3 volts at the battery while running, 14.4 volts at the alternator, no dimming of lights or starting complications? 2018 ford F-59

    • WheelScene profile image

      WheelScene 

      2 years ago from U.S.A.

      Awesome detailed post, thanks for sharing!

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