Why Is the Heater in My Car Blowing Out Cold Air and Not Heat?

Now that the cold weather is back, we'll be whacking the car's heater on the second we turn the key. Your car's heaters work by using the heat in the coolant that circulates around the car's engine. That's why you won't get heat until the car has been running for a couple of minutes and warmed the coolant. A thermostat regulates the water circulation; it waits until the water reaches a certain temperature, and then lets the water circulate to cool your engine, and incidentally warm your heater.

To have heat, you need:

  • enough water in your engine;
  • a working thermostat,
  • a working heater and heater controls
  • a cooling system that doesn't leak.

If you can't get heat no matter how long you leave the car running, I'm going to show you some checks you can do to find the culprit. If you're not comfortable with mechanics then read still read on so you know what to expect when you take your car to a mechanics. This problem is relatively cheap to fix. Replacing heater matrix's or head gaskets are where the costs become high.

1. Is There Enough Water in the Car?

Your heater uses the heat from the coolant circulating around the engine. You should also have Antifreeze in your coolant mixture, this not only stops the coolant from freezing inside your engine but also stops it corroding. The heater is higher up than the rest of the cooling system, and thus last in line for coolant. Thus the first thing you should do, if you have no heat, is to see if there is in fact enough coolant in your engine. You can do this by lifting the bonnet (the hood) and looking at the header tank, which collects overflow coolant from the radiator. This is a large tank, usually clear plastic, with a conspicuous cap, rubber hoses coming off of it, and "Max" and "Min" markings on it. It is positioned a little higher than the radiator, usually to one side or the other of the engine, directly above a wheel. If this tank is empty, you can fill it back up with ordinary water; you can add some antifreeze if you want. If your header tank is full then proceed to the next step. If you are not certain which is your header tank, ask a friend, or take the car to a local garage.

2. Is Your Thermostat Working?

As mentioned before, the thermostat decides whether to let water circulate around your engine. When the engine starts, the thermostat stays off for a while, giving the water a chance to heat up and provide heat for your heater. If your thermostat is stuck, the water may never heat up. So if you have water/coolant topped up, but still don't have heat, a broken thermostat may be the culprit.

To check your thermostat, leave your engine running and watch the dials inside the car. There will be one that indicates water temperature. It can take a while for a working thermostat to be warm enough to give you a reading, so give it about 10 minutes. If after that, your engine is hot, but your temperature dial says "cold," then the thermostat is the reason why you're not getting heat from your heaters. This is a simple fix, and it should be cheap from your local auto shop.

3. Is the System Blocked by an Air Lock?

Sometimes even with water in the system and a working thermostat you can still get no heat; the flow of water in the heating-and-cooling system may be blocked by air or dirt.

One possible cause is an air lock in the cooling system. If your system has a bleed port or bleed screw, and you can find it, you can fix this air lock yourself. Run the engine until the fan kicks in. Once your fan has come on, look around the radiator for a bleed port or bleed screw. This is something that can be turned with a screwdriver. Once you turn it anti-clockwise, you should hear a hiss; this is the air being released.

4. Are the Heater or Heater Controls Broken?

Even though most problems with the car heater are not caused by the heater itself but by the cooling system or the thermostat, it is still possible the heater itself may be clogged or broken. Or the heater controls may be stuck or broken. In either case there is a chance of a cheap or do-it-yourself fix, as shown in the video below.

Toyota Heater and Control Valve

5. Water Leaks? Find Them!

An engine that keeps losing water is a big problem, and not just because low water levels will keep your heater from putting out enough heat. A car that is not gettting coolant will heat up and damage itself permanently. If it leaks water, you need to find the source. It can be a split hose, leaky radiator, the water pump, or even worse, the head gasket. Finding the leak can be a pain in the butt too, as even a tiny hole can let a lot of water out while the system is under pressure from being driven.

But if the weather is cold, that makes your investigation easier. Make sure the engine has run long enough to get good and hot, and make sure the coolant is topped up. Then, if there is a leak, the hot water escaping will turn to steam when it hits the cold atmosphere. Open the bonnet (hood) and look for steam: along the hoses, where the water pump is, and along the radiator. Also look inside your car—if your windows steam up, or the carpet inside the front of your car gets wet, your leak could be inside the car, behind the dashboard. It could be the heater matrix itself (the heater core) or a split hose.

If the leak turns out to be in the radiator, you can save the cost of a radiator, at least for a while, with products that stop leaks in a car's cooling system. You can also buy a repair bandage for leaking hoses, but this is a temporary measure. Hoses are rubber and don't last forever; they have to be replaced every few years.

Sometimes water loss is caused by a knackered water pump. Telltale signs of a broken water pump include a constant rough metallic sound when the engine is running, or water trickling down the side of the engine. The water pump is a vital part of the engine, and if it's broken it needs to be changed as soon as possible. Often it runs off the cam belt ("timing belt"), and if the water pump destroys itself it will take out the cam belt and the engine along with it. Consider replacing an old water pump as part of routine maintenance, along with the replacement of the cam belt and accessory belts, if you have an old car and want to keep it a few years.

A leaking head gasket is the worst news at all; it means your engine has lost its integrity, and your car needs major repairs right away, assuming you want to keep it.

I hope you found this article helpful! If so, make my day by hitting the Facebook "Like" button on the right.

Simple Hack

A simple hack that I use do to get heat in to my heaters more quickly. I do this by placing some cardboard in front of my radiator. Place cardboard in front of the radiator and behind my front bumper. This is to stop airflow through the radiator, thus heating up your coolant more quickly. If you live in a cold part of the world or have cold winters this hack will help getting you coolant more quickly.

I do not completely covermy radiator, I allow it to get some airflow but I use a piece of card sized to restrict a large portion of airflow. This is something I have to do in the winter months. If I don't do this it takes a long time for the coolant to reach it's optimum temperature and as soon as I whack the heating on, the coolant temp falls. This because of the cold weather and the efficient airflow cooling of the vehicle.

You can use this simple hack as a temporary measure. Remove the card in the summer months. If your fans regularly come on remove the card also. Keep an eye on the temperature needle. If it sits a little high, reduce the amount of card or remove it all together.

Comments 63 comments

Karen Wodke profile image

Karen Wodke 5 years ago from Midwest

My heater blows out cold air. Except in the summer. Then it blows out hot air. However, if I let it run long enough, it does blow hot air. Anyway, I just posted this comment because I knew you wanted to know what my car heater does, but you probably felt a little funny about just coming right out and asking.

tcfsu profile image

tcfsu 5 years ago from Tallahassee, Florida

Very informative hub, thank you!

beckyboel profile image

beckyboel 5 years ago from New York

I have learnt a lot from your hub! Thanks a lot!

belko002 profile image

belko002 5 years ago from Atlanta, GA

Hah...This is too funny. I've been having this problem but had no idea how to fix it.

Thanks so much for the help.

If you had to suggest on and only one product, which would it be?

JP993 profile image

JP993 5 years ago from England Author

Thats great glad it's helped.

Belko002, it depends what symptoms your car has, if your heaters get hot if you leave the car running for a while, whilst stationary then you need a new thermostat for your particular car. If your water tempreature needle doesn't move when driving is also an indication the thermostat needs changing.

yaseen hoookpk 5 years ago

Am going to fly in this car today


just kidding.......

I hope i can see flying car in my life

JC 4 years ago

For the last 5 years my van has only seen warm temperatures

I had to stay the winter this year and the van blows cold air and the engine gauge heads to high and then if I hit a bump it goes down and it starts blowing warm air and everything is normal. What do you thinks is the problem? Do I have a stuck thermostat that unsticks when I hit the bump?

JP993 profile image

JP993 4 years ago from England Author

Thermostats are really cheap and simple to change so It would be worth changing to see if this makes the heaters operate correctly.

Your vans symptoms are a little odd though. If when you hit a bump, the gauge goes down and the heaters start to work then it means that the water is then able to circulate, which could be, yeh, the thromstat or it could be something else like an air lock in the system.

Look around the radiator and look for a bleed valve. Run the engine until it's hot and bleed off the air in the system. This costs nothing to do and might solve the problem. As above thermostats are really cheap so worth just changing also. It's a little worrying the car gets so hot, you're running the risk of popping the head gasket, the engine can pink which will start to destroy it ( poor fuel economy will be an indicator of this ) so you should try and sort this. Also if you leave the van running does the fan not cut in? Hope this helps.

aminah1801 4 years ago

Hi, i have found you site helpful! I find the water in my engine lasts approx. a week before my heaters start to turn cold. i also have a constant stream of whiteish coloured smoke comung from the exhaust. any tips on what it could be?


JP993 profile image

JP993 4 years ago from England Author

It sounds like Your Headgasket has gone by the sounds of it Aminah1801, especially as you're losing water after a week and you're getting white smoke out of the exhaust. There is a way of seeing if the headgasket has gone without taking the head off. Take your car to a garage and they'll be able to tell if your water is oil mixing with the water coolant, if it is, then this means you have headgasket failure. I wouldn't drive your car anymore until this is fixed. You could completely destroy the engine if you do.

kristen schmitt 4 years ago

I have had my car about four months and I noticed this November that the heater only blew warm air never hot, tonight while driving home it was blowing freezing cold air and the temp gauge went all the way to hot. Also it has been running really rough when I first start it.

JP993 profile image

JP993 4 years ago from England Author

Kristen, Check you have any water at all in your tank now, It sound's like its gone! Your water pump may have gone or worse case, your headgasket has popped.

Check your water level atleast and get some water back in it immeadiately. When you refill it with water run the car and see if it leaks out anywhere. Don't drive your car anymore until you've got a mechanic to look at it.

JT44 4 years ago

I had some luck with my old Escort, I had a leaking heating matrix? it was getting damp inside especially on the windscreen. A friend used a tiny bottle of Kseal and it looks like it has done the trick. Their site:

Willlow 3 years ago

Great article, but what about the actuator motor and the blend door? I didn't have heat in my vehicle and after some digging around, I found that the blend door was broken.

Joan 3 years ago

just changed thermostat still not heat only blows out cold air, so what's the problem.

JP993 profile image

JP993 3 years ago from England Author

what car have you got Joan?

Did you do the checks,

Temprature needle moving,

water in the system,

If you temprature gauge gave a reading before you changed it then the thermostat would have be fine. You would only need to change the thermostat if the you was getting little to no reading on the gauge after the car running for quite some time.

So you now definitely have a working thermostat. I'm assuming the water was topped up when it was changed, so you should be getting some heat atleast.

There are certain cars that are prone to having faulty heater matrix. Clio's were common of this for example. Make sure you check your footwell for dampness. Make sure all your settings are turned to heat.

If you have an older car and the problem was their befor e you got it, it may be that someone has blocked the heater off due to it leaking etc.

Michael 2 years ago

My car a Nissan Pathfinder 2002, the hot air isn't working. I already checked if the radiator had enough water and I also checked if the windows of the air system are functioning. The temperature of the car in the meter is normal when the car is running.

Is it possible that the thermostat is bad even though it's marking a regular temperature in the meter?

bryan 2 years ago

Check your heater hoses going to your heater core by the firewall. If one is hot and the other is cool your heater is plugged up. This does not mean the heater core needs to be replaced. It may be flushed out and you will get good heat again. This service will need to be done by a qualified shop. Reverse flushing the heater core needs to be flushed with water and air pressure. If both heater hoses are hot it may in the air distribution box which may be a cable or actuator. Unfortunately there is no easy answer, get it checked before the cold weather hits because then its tough to get into a shop. I hope this helps.

Teresa 2 years ago

Hi. I don't have any dials in my car. The heater is blowing cold air, won't warm up. There us a sound from the engine like a fan running (this is a new sound) and cold air is coming off the engine. I can't get the coolant tank open but it looks full. This car has been mistreated. I don't understand which hoses to check. Any help would be appreciated.

tyrissa 23 months ago

My heater gets hot then gets cold...what's goin on??

said 23 months ago

hi i have dodge neon 2000. the heat was working fine till this winter it blows cold little but you can feel the heat coming out but not enough even if you max it out .thermostat its fine,coolant will fill it again today ,so could think of something might hold the heat t come out properly .thanks

gladys 21 months ago

My nissan altima only lets out cold air when I turn the heater on. The heater only seams to work when im going at a fast speed. But once I slow down it stops working.

sweetz 21 months ago

My car is blowing cold air when heat is on, I had thermostat changed, radiator flushed, full of antifreeze and nothing happens. I notice a couple times the passenger side gets a little light heat when driver side don't blow at all but this is during fair weather. My trunk gets wet but by the lock end.

ron 20 months ago

no heat on driver side.t stat changed couple years ago.and where is the blend door on this 2003 accord

MeLinda 20 months ago

Hi. I have a 2002 Jeep Liberty. The heater used to blow nice hot air and then barely warm air. Temp gauge shows a little less than half way. Radiator, thermostat, temperature control module have all been replaced. Heater core has been flushed. Was driving and heat was barely warm and then started blowing very cold air. Busted radiator hose. Replaced. Still blowing ice cold air and now smoke is coming inside of vehicle.

CptKD 20 months ago

Apologies - My comment posted before I had it completed. . .

As I was saying - I appreciate that it was an easy read, and included instructions that were similar in nature, in that they were easy to follow. The manner in which you prioritized the possible/potential problems was also beneficial. I endured 2 days with no heat in the car, and it was brutal. Nasty as all get out, in these minus -15°'s and that's in the day. Throw in the wind . . . I figured out the problem - A new hose and clamp! A top up of water/coolant - I am Rock'n & Roll'n with HEAT! Like HOT! ;+) I'll be saving this page! Thanks again! √

roberta mcclain 20 months ago

My mechanic ran a test said it was a head gasket bye van can't afford to fix it. I'll be riding a bike

kane 19 months ago

Hi just wondering if u could tell me if i have removed my air conditioning unit would tht stop me getting hot air out of my heater my temp gauge reads normal halfway but no hot air

kane 19 months ago

My air conditioning unit has be removed so would this stop my heater blowing hot air? If not what could it be my car always reaches normal temp so cant be the thermostat rite?? Could it be air in my radiator or something... thank u

adam owens 19 months ago

Thank you so much can't wait to wake up and get started!!!

Monica Madrid 14 months ago

It blows out just cold in both why

Rose Mitchell 13 months ago

I have a 2000 Dodge Caravan i replaced the thremast top off the fluid and i have no heat just cool air blow's out the temperature gauge reads normal what could it be?

John k 12 months ago

2002 ford explorer. Clunking / banging noise that changes tone or goes away when adjusting temperature knob. Engine temp is normal on gauges, but most of the time still blows cold air.

Lauren 12 months ago

I have a 2000 dodge caravan. The heat and air blower comes on and works but its just air. We know the switch for where it blows is stuck on the defrost vents but thats a later issue. The main issue is getting the heat to work. We are going to try to flush it first bf the heater core but wanted to ask in case there is a quick fix

JP993 profile image

JP993 11 months ago from England Author

John K,

You could have a broken heater matrix, the bearings in the fan could have potentially failed.

Rose and Lauren,

Sounds like there is a common issue with 2000 Dodge Caravans. Heaters on these cars need to be recalibrated from time to time, a garage should be able to do this. The mechanisms are also mechanical which change air from hot to cold. These may be warn.

Irene Galligan 10 months ago

Hi I own a 2003 Mitsubishi Lancer heat was fine until 3 yrs ago. The black button turns left easily for cool air but won't turn right for heat. I did some research found many others who had the same problem. I brought it to one mechanic who said he would have to remove the entire front console to fix it. This would cost a lot like $1000 which I thought was crazy so I gave up. My son drives it now I beg you can you tell me what I should do to fix it. Thank you.

JP993 profile image

JP993 10 months ago from England Author

Hello Irene,

This sounds like a mechanism problem which would require removal of the heater matrix. $1000 sounds a lot but this could be a very labourious job. Not difficult just time consuming.

melinda 10 months ago

My truck is a 2011 chevy colordo and the heat or a/c will work. It will not blow and the blower is good the heater coil is good. We dont know what esle to do

Cindi Best 10 months ago

My car is over heating and heater blowing cold air changed thermostat not leaking any fluids no fog or wet floor it only over heated once then i parked it could this still cause sirious damage

Luc Gratton 10 months ago

I set my heat control to high, the fan to high, in the morning I start my car from the house with the remote starter, after 15 minutes I go in my car and sometime the air coming from the heather is cold, if I turn the heat control to cold and then back to hot then hot air come out, my garage change the motor and adjust everthing and it happen again sometime, they don't know what to do anymore, it is quit frustrating on a cold morning

Margie 10 months ago

I need help as my heater is putting out cold air. I know the switch is broken and if i switch it just right it cstches and out comes hot air. Well the other day i changed it subconsciously and now cant get it to catch back. I do not have 500.00 right now that the mechanic says it will codt to pull the dash and fi . Is there a quick cfix for now? Thank you.

Jeanna 10 months ago

I replaced the thermostat put antifreeze cleaned the radiar and it still blows cold air i have a 96 saturn

JP993 profile image

JP993 10 months ago from England Author

Cindi you may have a head gasket issue. Take your oil filler cap off, see if the oil is creamy or have a garage test for oil/fuel in the coolant.

Ashley K. 9 months ago

Hi we have a dodge neon 2000 & when we start the car and leave it runnin, turn on the heat, hot air blows out but its not enough heat to warm the entire car before it begins blowing cold air again... We've replaced the thermostat, addded coolant, checked the radiator and controls, but we can't seem to find the problem nor fix the "no heat" problem

Any ideas as to what we could do or look at to find the problem? & how to fix it? Thank you!

jarrett 9 months ago

I just changed my thermostat in my dogde derango it blows light heat out but then blows out cold air again what can be fhe matter

JP993 profile image

JP993 9 months ago from England Author

Hi Ashley and Jarrett,

have you tried flushing the coolant? there could be a blockage.

Austin 9 months ago

I have a 2003 Mazda 6. I let the water temperature get warmed, and my heat works, but after about 5 minutes of using it, it'll blow cold air and the water temperature gauge drops back down. Once I turn of the heat it'll rise up again and the cycle continuous

araceli 9 months ago

Hi! I have a 2005 Chrysler Pacifica and the left side of my car's heater blows out hot air and the right side cold. Do you know what the problem might be?

Matt 9 months ago

My nissan heater only throw hot air when it's moving. When it's on park or at a stop sign it throws cool air... can someone tell or explain what's wrong

Martine 8 months ago

I have a Nissan sentra 2004. When starting it cranks but takes a while to start you have to pump the gas to help it start. Secondly the heater does not work, blows cold air. When you drive it jerks and when you stop at traffic light it it rocks back and forth and on acceleration you need to step the gas slowly otherwise it will lose power - it drives on slow speed. I took it to Evans automotive and they said the problem is; the sensor is terminated at the wrong end, there is a head gasket which blew due to overheating, but i have never experienced over heating on that car. It does not overheat now. One of the things they said was the coolant was empty, i checked the radiator and it had not water. Yet previously I had put in antifreeze. So i filled some water on the radiator, them i saw steam coming out of the engine. When I opened the bonnet I found coolant and water spewed all over the engine. I poured water again and I saw the leak of top of the radiator edge. Now it the the diagnosis of Evans correct or they did not see the problem with the Radiator. What exactly is the problem and what should i do first?

Shay 8 months ago

thank you very helpful. Where is Facebook like ?

tsadjatko profile image

tsadjatko 8 months ago from maybe (the guy or girl) next door

You do know millennials will read this, you forgot the most important of instructions that they need to know.


Great hub page! Must keep for future reference.

nick 7 months ago

just bought a 01 astro and tonight for the first time out of no where i lost heat added anti-freeze and got heat back but i dont know where the water is going no leaks as i can see and runs like a champ? it does have rear heat but dont know if any leaks r in those lines

Ben 6 months ago

I have a 1997 honda civic lx 1.5 5 speed and it blows cold air and overheats. It has a new timing belt and water pump. Semi new head gasket and thermostat and the radiator was just flushed. Any ideas?

robert 5 months ago

My car no matter how long it runs still blows cold air and win the water timp gage goes up just a little as sewn as I turn it on it hose down I would like to no the problem

DEAN 5 months ago


bill 4 months ago

I didn't read all of the posts so this may already be in there. A stuck thermostat is the most likely culprit. However, it can stick open resulting in the water never getting warm enough to supply warm air to the interior or it can stick closed resulting in the car overheating. The above BMW problem could be a thermostat or vacuum leak. Vacuum holds the heat door open or closed. When you let off the gas, you supply enough vacuum to allow the heat door to open and when you give the car gas, the door closes.

Leecia 4 months ago

Well this helped alot... i do have a water leak on my Jetta 4 and i figured the heater is not working because of that... this confirms it.. i need to get it sorted out asap.!!

Phil 3 months ago

I've got a 2000 Mazda Familia 2 litre Diesel. Radiators full, gauges work, new thermo' , water circulates but got only very low temperature heat.

Flushed it out 3 times over the last few months and still no heat.

Some years ago I had a slight leak from the water pump and put a "stop ;eak" stuff in. Could this be the problem and if yes how do I now sort it?

Ashley 2 months ago

OK so my problem is I have a 2001 Chrysler town n country 3.3L. I have to put water in my van every day I don't see any leaks besides when my air is on. My heat does not work it blows cold air and the heater and air only work on high. It use to work months ago on every setting but always made a really loud noise when on until it only worked on high still make a kinda loud sound. I have checked for leaks but can't find any. Just not sure where all the water goes so fast with no leak. I'm temp gauge works great I had replaced the radiator cap not long ago and my fuel cap because my check engine light was on saying there was two leaks I cleared the codes after I fixed both and check engine light hasn't come back on... I'm so lost any suggestions would b great thank u

s.rose 5 weeks ago

Very helpful article, specifically the workings of the thermostat and coolant.Now i know if the thermostat stays open, you suffer (no heat) and if it stays closed the engine suffers, it doesn't cool off.

Amanda 10 days ago

My 2005 Toyota Matrix X-rays. My heater is not that hot on the driver side and on the passenger side car in t is cold. Can u please tell me what the problem of s. My car does not over heat. The hoses going to the heater core r hot under the hood and they r hot in the cabin. Need help please

Ben 9 days ago

Very helpful, I bought a new thermostat for my 2002 Hyundai Accent and it warmed my heater and brought the temperature gauge to operating temp

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