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Why Your Car Won't Start When Cold and What to Do

Freezing temperatures can zap battery power in minutes.

Freezing temperatures can zap battery power in minutes.

What Freezing Temperatures Can Do to Your Car

Here are the three main reasons freezing temperatures can keep your car from starting. When it's cold:

  1. Battery performance goes down. Cold temperatures slow down the chemical interaction between the battery electrolyte and the plates, reducing battery power. This means that battery current decreases as temperature decreases, starving the starter motor of much-needed power.
  2. Engine oil thickens. At the same time, engine oil turns into a syrupy substance that won't flow as easily, much less through small clearances of around 0.002" (0.05mm) within the engine. This sluggishness causes too much friction around components that need to move at high speeds.
  3. The engine's need for power increases. As the temperature goes down, engine demand for starting power increases. Low temperatures stress mechanical components. Since oil won't flow easily, crankshaft, pistons, and valve train components will experience higher friction.

As you can see, battery operation, oil efficiency, and engine mechanical performance all have one thing in common: They all need an adequate temperature to start working without problems.

The following graphic can show you this relationship more clearly.

In lower temperatures, the power needed to start the engine increases, while the efficiency of the battery decreases.

In lower temperatures, the power needed to start the engine increases, while the efficiency of the battery decreases.

On top of these effects, your battery's age, plus poor maintenance or wear of components in the charging and starting systems, will affect the engine's ability to start at freezing temperatures.

Note: If It Cranks But Still Won't Start

If at cold temperatures your engine turns over at its normal speed—or close to it—but won't start, your problem may be in the ignition system (worn spark plugs or wires) or fuel system (clogged fuel filter, or frozen droplets of water in the fuel line).

In This Article: How You Can Help Your Car's Engine in Freezing Weather

I. How Can I Start My Engine in Cold Weather?

  1. Check the battery
  2. Check battery connections
  3. Check battery electrolyte
  4. Check the battery and solenoid for voltage
  5. Increase battery temperature
  6. Replace the battery

II. Help Your Car's Engine Cope With the Freezing Winter

Freezing temperatures can zap battery power in minutes.

Freezing temperatures can zap battery power in minutes.

I. How Can I Start My Engine in Cold Weather?

There's little you can do to immediately reverse the effects of cold weather on an already ice-cold engine. But here are a few things you can do that may help your engine start.

When you try starting the engine, it may not turn over, meaning the engine doesn't move at all. You may hear instead a series of clicking noises. This could be a sign of a discharged battery, loose or corroded battery cables, or some other starting system problem.

1. Check the Battery

  • Turn on the headlights. If they are bright, almost normal, you still have some battery charge; if not, the battery charge may be low. Continue with the next steps.
  • Turn the ignition key to the On position for about 8 seconds, but don't start the engine. Repeat the process one or two more times and try to start the engine. Fuel pressure may need a little help.
  • If nothing happens, take a look under the hood. If you see signs of corrosion around one or both terminals, or they feel a little loose when you twist them, that could be your problem. Remove corrosion from the cables and terminals (see the following section), or tighten the cables with a wrench.
  • If everything seems fine, probably the battery has run down. If your battery is good, try jump-starting the engine. Ask a neighbor, friend, or car shop to help you start your car. In most cases, this will get you moving. If your vehicle has specific jump-starting points, consult your car owner's manual.

Warning: Don't Charge a Battery When Frozen!

Don't try to charge a battery if you think it is frozen or has ice in it. This can burst the case open or cause an explosion from internal pressure. Allow the ice to melt and the battery temperature to rise before you start charging.

2. Check Battery Connections

During the summertime, you may get away with a little corrosion between the battery terminals and the battery posts. Not during the winter. Corrosion acts like electrical resistance, and you need every bit of juice you can squeeze out of your cold battery.

Sometimes, corrosion hides between the inner side of the terminal and the battery post. If you haven't checked the terminals recently, now is the time:

  • Disconnect the battery terminals (the negative terminal first, then the positive side) using a wrench.
  • If necessary, prepare a solution of 8 oz. of warm water and a tablespoon of baking soda in a disposable cup. Thoroughly mix the solution.
  • Dip the battery terminals in the solution for a few seconds and use a soft brush to remove corrosion from the terminals. If necessary, use a wire brush to remove corrosion.
  • Use the soft brush to clean the battery posts as well. Wipe the posts clean with a clean rag.
  • Also, wipe the top of your battery clean, if necessary. Using the mixture of warm water and baking soda, apply the solution with a soft brush and wipe it clean using a clean rag. Don't allow the solution to seep under the battery caps.

3. Check Battery Electrolyte

  • On a battery with removable caps, wipe clean the battery top with a shop rag to prevent debris from falling into the battery cells before removing the caps.
  • Remove the caps using a flat-head screwdriver and check the electrolyte level.
  • The electrolyte should reach the bottom of the filling rings. If not, add the necessary amount of distilled water to each cell.
A worn starter motor may fail to run under freezing temperatures.

A worn starter motor may fail to run under freezing temperatures.

4. Check the Battery and Solenoid for Voltage

Sometimes, the problem is that either your battery or a connection in the starting system is preventing the necessary current from reaching the starter motor. If so, your engine won't crank at all when you turn the key to start the engine. If this is happening:

  • Check that your battery has 12.4 volts or more. Measure battery voltage across the battery posts with your voltmeter. If you get less than 12.4 volts, you need to charge your battery.
  • On the starter solenoid, connect your voltmeter red lead to the S (starting) terminal, and the meter black lead to battery ground (-). You should get at least 12 volts when you turn the ignition key to start the engine; otherwise, there's a loose or corroded wire along the way in the ignition part of the starting circuit.
  • If everything seems fine at this point, it's a good idea to do a voltage drop test on the system. A starter-system voltage-drop test is a more accurate and faster way to a fault in the circuit in the starting system. Don't forget to do a voltage-drop test on the ground side of the circuit as well. Many circuit problems are due to poor grounds.

Check the charging system as well, if necessary.

5. Increase Battery Temperature

If possible, you can try removing the battery and bringing it indoors to warm it up.

  • Disconnect the negative battery cable first and than the positive terminal from the battery.
  • Disconnect the battery hold-down or retainer.
  • Bring the battery into a room, away from the cold weather, and wrap it in an old blanket or cover for a few minutes to bring its temperature up a bit.
  • Reinstall the battery and try starting the engine.

6. Replace the Battery

As your battery ages, its chances of coping successfully with cold temperatures diminish as well. On average, a battery's service life is four to five years, though some manufacturers recommend replacing the battery every three years.

If your battery is already reaching the end of its service life, you may want to install a new battery now. A brand-new battery has a better chance to withstand cold weather and help your engine fire up.

Use an electric block heater for cold weather starts.

Use an electric block heater for cold weather starts.

II. Help Your Car's Engine Cope With the Freezing Winter

To avoid getting stuck during the freezing months of winter, there are several things you can do. Buy special car accessories, make sure you have adequate tools, and prepare your engine for the chilling temperatures ahead of time.

  1. Your local or online auto parts store may carry special accessories and tools that can help your car survive the winter months. Some things you may want to consider:

    • battery blanket
    • electric engine warming blankets
    • oil heater
    • block heater
    • battery booster
    • battery (trickle) charger
    • jumper cables
    • winter emergency kit
    • carport

    Yes, even a carport will help to keep your car a little warmer during a snowy night or day.

  2. Use the appropriate engine oil for the winter months in your area. Consult your car owner's manual or your local car shop, dealer, or auto parts store. For example, if you use 10W-30 engine oil during the summer, you may need to switch to 5W-20 for the winter months, or even a 0W grade (a very thin oil) especially useful in freezing cold, sub-zero temperatures.
  3. Make sure the coolant has the correct strength to protect your engine from the freezing temperatures in your area. Consult your car owner's manual, your local shop, or an auto parts store.

    A 50/50 mixture of antifreeze and distilled water is appropriate for most weather conditions. But you need to make sure your antifreeze has been approved for at temperatures least 20 degrees lower than the lowest temperature in your area. For example, if the normal lowest temperature in your area is around 20 F (-6.6 C), your coolant should have a freeze-up point of 0 F (-17.6 C).

    You can use a hydrometer to test your coolant. You simply draw coolant into the tool's reservoir by squeezing a rubber bulb and the tool will show the current freeze-up protection of the coolant in your vehicle. Follow the instructions that come with your tool.

  4. Keep your fuel tank over half full during freezing cold temperatures. This minimizes condensation and the chances of clogging fuel lines. This may be less of a problem than it used to be, as anti-icing agent is added to gasoline now to avoid fuel line freeze-up during the winter season. If the gas you are using doesn't come with this additive (check at your gas station), you can buy a bottle of "dry gas" at your local auto parts store and add it to your tank.
  5. Service the charging, ignition, and starting systems as necessary.
    • Check the battery. Make sure the battery is clean and has enough electrolyte.
    • Inspect the belts. A good and properly adjusted drive belt is critical for the operation of the alternator.
    • Check the charging system operation. Make sure it is properly charging the battery.
    • Check the starting system operation. Inspect the starting system connections and look for signs of corrosion and loose wires that may prevent the battery to deliver power to the starter motor.
    • Check the ignition system. Make sure you are getting a good spark. Replace spark plugs and wires as necessary.
    • Check battery and engine grounds. Loose or corroded engine ground connections will make it difficult for current to get through.

The following video shows how using a heating pad can help you start your vehicle when it is cold.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2019 Dan Ferrell