Heater not working

check heater hoses to make sure they are hot. make sure coolant level is full, then check the actuators under the dash to see if they are working.

This guide can help us fix it

https://www.2carpros.com/articles/car-heater-not-working

Check out the diagrams (Below). Please let us know what happens.

i was useding my air conditioner in the pass and when it got cold i had no heat my i think condenser and air con. hose would be dripping water with the heat on is there a relay or vacuum to switch it back n fore i hope u can help

The heater won't cause condensation; thus, there will be no water dripping. Make sure the radiator is clean and full. If both heater core hoses get hot, make sure the blend door is working. If only one gets hot, try flushing the heater core.

When the gauge was on the hot side all that I was getting was cold air. I watched the gauges to see if it was over heating. Everything was right. Is the gauge that controls the hot and cold side need to be replaced?

Thank you for your help,
Duane

With the engine at full operating temp, locate the 2 heater hoses where they go into the firewall and feel them to see if they are both hot to the touch. If they are..........

The temperature is controlled by the use of an air mix door that is operated by an electric motor/actuator. This door can be jammed or the actuator can be inoperative or have stripped plastic gears internally.

hose on the passenger side - hot
hose on the driver's side - cold

please advise

blowing cool air, had it flushed and still blowing cold air. Its not over hearting and runs great.

Could be the thermostat, clogged heater core, heater control valve and door problems not switching within air mix/blend/mode positions,vacuum and actuators to include the HVAC control module.

That means that your heater core is plugged up. You can try removing both hoses and flushing out both ways with a garden hose but you may end up having to change the heater core and that is a real big job.

not sure if I have one issue or two. 2004 Chevy blazer, heater blows cold air ( pronoun initially random and only occurred about every 3rd or 4th time I started vehicle, gradually became worse over a month or so, now only blows cold air. additionally, during warm weather, air conditioner blows good cold air, however auto overheats if outside temperatures are above approx. 75°. Turning air off does little to help reduce overheating. Have replace thermostats 3 times, replaced water pump and have had radiator flushed and checked out by a mechanic. Was told no issues with radiator. Not sure what issue is out where to turn next. Is this a common issue?? Could it have something to do with heater core? Do I have two separate issues or are they related? if any idea on problem, what is estimated repair costs? Appreciate any assistance. Mammastone

when hot check rad for cold spots if there are any rad is bad it should be sametemp all over. then have coolant system pressure checked for internal leaks.

My heater seems to work internmittently. Sometimes it is really hot and sometimes not at all. The other day it was too hot so i turned the temperature down and then it got cold and when i turned it back up again it would not get hot again. I purchased this car in mid-summer this year and know that it has had a fornt end accident in its history.

Sounds like the mode door control motor is failing or the door itself has a problem. It is possible to give it a rough test by listening REAL close and having someone disconnect and then reconnect the battery. The mode door will cycle open/closed.

Could also be the vacuum control assembly. For that one you apply vacuum at the line into the body. Test it for leakage and move the control at the same time. You should hear the doors move as you move the controls.

I had to have fan motor under dash replaced. air blows out top vents and windshield.
But nothing on feet. no heat or air on feet. I called one mechanic he said it would cost
$800 have take whole dash out find problem. It that what has to be done to fix?
Thanks Mike

check for a vacuum leak the mode actuator may have hose disconnected or one by the blower does. also check behind control unit. anyone of those can cause it . it can even be disconnected in engine compartment.it's a small thin line see pic.

Recently when driving, less than ten minutes the engine will overheat almost to the max red line. I turned on the heat, and no hot air comes out, it just blows cold. I was on my way to work and kept going, then the temperature gauge dropped to 3/4 (still 1/4 way to max hot) and stayed there. The first day lots of steam came out before it cooled. Now steam is not coming out, but all other issues remain. Is this just a thermostat, or likely something else?

low coolant will not circulate through the heater core and this is why you have no heat, you need to get a cooling system pressure test done to locate any external leaks first. top up the coolant as if it is to low you run the risk of doing serious damage to the engine.

Hello JENERAL,

If you decide to conduct the test yourself here is a link to a helpful and informative article from this site. This article features a step by step guide, pictures and a video on how to pressure test a cooling system.

https://www.2carpros.com/articles/radiator-pressure-test

Thank you for visiting 2CarPros.

All the best,

Renee
Admin

When the car is 1/4(Gauge) warm to 1/2 heater air is warm. Once the car reaches normal temp. the air is cold if the rpm drops below about 1700 rpm. Heater core is not clogged, runs freely and hoses are same temp. in and out.

Replace the thermostat-don't work come on back or you can start checking the air mix/mode/blend doors if their opening could also be vacuum and actuator problems.

My 2003 Chevy blazer heater stop working but the ac still works fine what is the problem so I can fix it.

First thing to do is check that you still have circulation with the heater on, both heater hoses should be hot with the engine at temp, check this and let me know what you find.

mark (mhpautos)

to fix the heat you need to start the test at heater hoses under hood
with engine running and at operating temp heater fan motor on high open hood and check heater hoses by the firewall
if both hot you have a blend door issue inside under the dash on the HVAC box
if one warm or hot and other not heater core need to be flushed
isolate heater core and flush
let me know

were to find the prolme

Can you describe what is happening with the heater? Does it work at all? With the engine running, hot, and the heater on high, do both heater core hoses get hot? Also, is the coolant full?

when I turn my heater on all it does is blow cold air.my tempture gauge tells me the car is gettin heat.I have antifreeze in the truck.just when u turn the heater on just blows cold air

Try replacing the thermostat and see what happens-if it continues -could be an air mix/blend/mode door problems-to incude vacuum/actuators and the HVAC control module.

k im dealing with a heater problem sometimes the the fan took a bit to turn on to blow the eat and then when the heat is goiing when i put it in park its not blowing hot air and when its just stopped and not ion park its still not blowing hot air

Hello, I'd check voltage and ground at the blower motor, purple wire is voltage, black is ground. First I'd make sure the blower motor isn't faulty, go from there.