Posts Tagged ‘bad thermostat’

My heater in my car does not work, what can I do?

Tuesday, October 20th, 2009

My heater in my car does not work, what can I do?

Have you ever been sitting in your car waiting for the heat to warm up?  Now just imagine that your heating system on your vehicle is not working properly.  You will be stuck with a cold car in the middle of winter.  If you do not want to be stuck frozen in the middle of winter, then this article is for you.

heatercoreTo check your heater system on your vehicle is extremely simple, and often overlooked.  I would recommend that you do the check before winter, preventing you from doing this outside in the cold.  I know most of us do not think of checking our heating systems in our vehicles before winter, but it is a good idea.  With winter coming up, now is a great time to do this check.


The Procedure

  1. First start your car and allow it to run until at proper operating temperature.
  2. Now you will want to turn your heat all the way to the hottest, and then turn the blower speed to one away from high.  This is the hottest air.
  3. Next you will want to choose the different vent locations and feel the air coming out; it should be very warm on your hand.

I am assuming that from this point on your car is not properly heating.  There are several simple things that may be wrong.  Checking these simple things will help prevent you from being extremely cold in the winter. 

Ok first we must discuss how your heater on your vehicle works.  The heater is much like your radiator in that it is a heat exchanger.  It is not like a household heater that has an electric element that heats up, unless however you drive a hybrid, some of the hybrids use a heating element.  The heater in your vehicle allows hot engine coolant to run through the core.  This coolant moves from the hot heater core to the cooler air passing through the heater core.  This then heats the moving air up.  The heated air is then blown out your vents using a series of passages under your dash and with the help of your blower motor.  The blower motor is fan that blows the air.

Now that we discussed how your heater on your vehicle works we will discuss some of the problems that occur causing a low heat condition.  Most of these problems are fairly simple to fix. 

Low Coolant

The first problem is your vehicle may have a low coolant level.  This means that there is not enough coolant flowing through your heater core, thus creating a low heat situation.  This is simple to check, first you will want to open the hood and check at the radiator overflow tank.  You will want to check the hot level because your vehicle is warm.  If it is low add coolant to the overflow tank.  After adding coolant you will want to run your car and then let it sit.  Remove the radiator cover and check the freeze point of your coolant using a Coolant Tester.   Do not add coolant or check coolant on a hot radiator.

Plugged Heater Core

Another problem that may occur is that your vehicles heater core may be plugged.  This will not allow the coolant to flow through the core causing poor heat.  To check for this problem it is simple.  First you will want to take your hands and hold on the two heater hoses going to your heater core.  These are located by the firewall.  Since your vehicle is warmed up they both should be about the same temperature and hot.  If one is not hot then you have a plugged heater core.  If you have a plugged heater core this could come from sealants being put into your radiator.  You may be able to clear the debris however.  You will want to remove the two heater hoses and take a garden hose, and spray into one of the hoses.  Hopefully the water will clear the system.  If not, then you may have to take your vehicle to a mechanic and have them try further.

Misadjusted Blend Air Door

The blend air doors allow a certain amount of the air coming into the vehicles HVAC (Heating Ventilation and Air Conditioning) system to go to certain places.  This will help regulate the amount of air on some vehicles that pass through the heater core.  This is a little more challenging to adjust.  You will need to get under the dash of the vehicle and locate the actuator that moves the blend air door.  You may have to look in the vehicles service manual on the specific location.  Once you have found it you are going to want turn the temperature from one extreme to the other watching the door move.  You will have to notice where it is coming up short in and adjust from there.  It may take a couple of times but watch the door move.

Worn Out Thermostat

A worn out thermostat can lead to poor heating of your vehicle.  This is because the thermostat regulates the flow of coolant in the engine.  If your thermostat is bad it just allows coolant to flow constantly.  This will lead to a cold engine due to over cooling and excessively cold coolant.  Since the coolant is what heats the air via the heater core, then with a bad thermostat your cold coolant will not get the vehicle hot enough.  To replace this check out this article “Replacing Your Thermostat”.

Damaged Heater Core

If all of your tests have passed, and you still have poor heating you may have a damaged heater core.  This could have broken fins or bent fins, or it may even just be plugged or leaking.  Regardless of this, you will need to take your vehicle into the shop.  The repair is very difficult most of the times due to the locations.     

I hope after reading these causes of low heat in your vehicle you will be able to fix the problem yourself.  A heater helps play a key role in the winter time, do not be stuck with poor heating. 

Written by: Cody Mammenga an NDSCS Student