Heater blows cold air part of the time

Hello,

This car does not have a heater control valve it sound like the temperature blend door actuator is not working which is common. Here are two guides to walk you through the problem and the location of the actors as well.

https://www.2carpros.com/articles/replace-blend-door-motor

and

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

Please run down these guides and report back.

Thanks for this post I had this problem and had to replace the actuator cost me $67.00 all fixed! I love this site

anti freeze is leaking and heater is blowing cold air. what do you think the problem is and how much should it cost.

thanks

jp

Where is it leaking and what is engine temp?

I have been trying to get my heater to work with no luck. At the relay by the resistor I am getting twelve volts in, but then when I test at the resistor it is a low reading. when I turn the switch from low to high and only two of the modes work. Is this a bad relay or is it something else? Dash control and roof control will not work. If I bypass the relay and jump it to the motor it will work.
Your help is much appreciated. Thanks,
Todd

when you turn the switch three of the resistors work that can be a bad resistor on high it runs through the relay to the blower the relay is under hood. check the switch as I do not know how many speeds you have I am assuming four.

There is a relay right next to the resistor and I was checking the incoming power to the resistor straight out of the relay and got five volts. The heater switch has four settings and three different control panels in the vehicle and none work. I switched out the AC relay under the hood. I have current going to the relay in the dash compartment and if I jump that to the resistor the blower comes on. Also, I noticed that when I press on the AC button or recirculating bottom the lights so not come on could this be the problem if these controls do not have power?
Thanks, Todd

it could be the control head which has to be scanned by a mechanic and or the relay for the blower. if you have a like relay try replacing it with that and see if blower works. you can also use the link provided on how to test the relay. But it may be control head which if you replace it will need to be programmed to your vehicle by a mechanic.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

There are three control heads in the vehicle and none of them work, but as I was saying I have only five volts coming out out the relay which is puzzling me. I thought if a relay was bad nothing would go through.

no, the control head may be supplying the five volts to activate it. and it is getting twelve on one side but not putting the twelve volts to blower. red wire twelve volts, orange five, blue twelve, purple wire to blower. other wire ground wire to blower will vary voltage depending on setting of speed. black wire ground. front control module supplies power to aux control.

Okay, so should I be looking for a control head? But why will none of the other ones work ? I am confused.

have a mechanic scan for codes as another control head will need to be programmed and you wont be able to do that. if this is auto temperature control then it really possible to be something else causing it.

So you think it could be the relay that ties in just before the resistor?

no, I sent a link on how to test a relay, but until you scan for codes you wont know what it is.

Hello, my heater will not turn on. Dash control and controls for the rear are inoperable. I checked the fuses and all good and switched out the relay under the hood. The resistor looks good, but could that maybe be the reason why the fan will not come on at all. And, there looks to be another relay behind the glove box by the resistor, is this part of the fan too? What should I do here I am freezing every morning!
Thanks, Todd

check items in picture. the blower relay for aux is in under hood fuse box so check there and one in picture is under hood as well.

i have no heat in the front unit but it has heat in the rear unit.everything seems to be working fine.it blows air but will not get hot.

Blend door p[roblem maybe actuator or HVAC controller

my heater is not blowing heat and temp is runnin bout 85 c

check to see if both heater hoses ar hot then check the accumaltor under dash for heat. onemay not be working. generic pic enclosed.

When the heater is turned off hot air continues to come out of the vents. The blower motor turns off correctly just not the air temperature. Any ideas what I can do ?

[quote:d8e19fca26="trinaarnos"]Heater problem
2001 Chevy Suburban V8 Four Wheel Drive Automatic 135000 miles
----------------------------------------------------------------
When the heater is turned off hot air continues to come out of the vents. The blower motor turns off correctly just not the air temperature. Any ideas what I can do ?[/quote:d8e19fca26]

you need to remove some of your dash and look at your actuators. I would say your mode door actuator isnt working to shut off outside air, its still blowing through the heater core

my heat is not working

I assume you mean the temp of the air and not the blower itself.

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 not too hot to hold, then you have to look at the actual engine temp and if that is up, if it is, then your looking at a restricted heater core.
If you find that they are both too hot to hold, then the heat in that vehicle is controlled by a blend door that regulates heated air flow. it is operated by an electric motor/actuator. The problem can be that the actuator is stripped or inoperative or the door itself could be damaged. This is what needs to be determined by examining the actuator and see if it is responding to heat change commands or not.
If they are both not too hot to hold on to, then you either have a restricted heater core or the system is not completely full and getting air pockets for some reason.