Heater being weird - thoughts?

[BeenChevy]

Good luck. I also agree the blend door actuator could be getting weak.. and slow to turn. If it does fail or you'd like a replacement I've got a brand new one sitting here that is let go for $20 shipped. Just double check the pn of the one you have in there.

 

[mizzouguy]

I sometimes find that when you set it to say 70 and auto, it will only blow out kind of warm air. Like its trying to put out 70 degree air from the vents using blend doors and air vent temp sensors. I sometimes put mine on 80 or high and switch to manual mode so that it blows hot air, and then once im comfortable I switch back to 70 or 75 and auto.

 

[Rocket Man]

I found out also that if you replace your battery or it goes dead, or if you replace any of the HVAC controls, if you don't follow the correct procedure the actuators can get confused. That's when the reset procedure needs to be used. Here's a link. http://www.tahoeyukonforum.com/threads/recalibrating-hvac.81057/

 

[Rocket Man]

I sometimes find that when you set it to say 70 and auto, it will only blow out kind of warm air. Like its trying to put out 70 degree air from the vents using blend doors and air vent temp sensors. I sometimes put mine on 80 or high and switch to manual mode so that it blows hot air, and then once im comfortable I switch back to 70 or 75 and auto.

I set mine at 70 and auto and it works perfect. It brings the interior up to 70 as fast as the engine warms up, and never blows cold air. The fan slowly ramps up as the engine warms.

 

[aces-n-eights]

Good luck. I also agree the blend door actuator could be getting weak.. and slow to turn. If it does fail or you'd like a replacement I've got a brand new one sitting here that is let go for $20 shipped. Just double check the pn of the one you have in there.

Excellent! Thanks. Dumb question... where is the blend door actuator and how do i check to see if it is operating properly?

 

[aces-n-eights]

The heater is still not working properly... It seems to consistently blow cold air for too long and then something happens and it works like it should.

Does anyone know of a troubleshooting or diagnostic procedure to help me run down what is going on?

Thanks!

 

[aces-n-eights]

Got my heater working properly and thought i'd add a post with the solution in case any one else has a similar problem in the future...

I also need to admit my "dumbassness".

The coolant was low. I open the hood and look around, check the oil and so forth on a regular basis. The coolant tank has a stain to it and i thought it was up to the proper level. It was not. I found a radiator leak and it appears the coolant leaked out to a certain level, still not to the point of overheating, but enough to make the heater not function properly. After a new radiator all is good.

So there ya go. Don't just look at the reservoir, open the cap and look inside.

 

[rockola1971]

From what I understand the compressor runs for a big to remove moisture from the air during defrost, it's not in a cooling mode.

It is running in a cooling mode. Thats the ONLY way it can remove the moisture inside the vehicle. ALL air conditioners really are just dehumidifiers. The air doesnt carry the heat, its the moisture (humidity) in the air that carries the heat. This is how all A/C systems cool. Your refrigerator, deep freezer, home central air, auto a/c are all dehumidifiers and the main difference is their cooling capacity between them all.

 

[Rocket Man]

It is running in a cooling mode. Thats the ONLY way it can remove the moisture inside the vehicle. ALL air conditioners really are just dehumidifiers. The air doesnt carry the heat, its the moisture (humidity) in the air that carries the heat. This is how all A/C systems cool. Your refrigerator, deep freezer, home central air, auto a/c are all dehumidifiers and the main difference is their cooling capacity between them all.

It only cycles on for a few seconds. Not long enough to actually cool but long enough to remove humidity. You can check for yourself; if you turn the temp to hot and have the blend set to defrost, open your hood and you'll see your a/c compressor cycle on for a few seconds then off. Over and over. And it's definitely not in a cooling mode, there's hot air coming from the vents.

 

[retiredsparky]

I have started having a similar heater issue, a random period that may last an hour or less or more,with one side being cold, the other side hot. I think I will replace the air temp sensor on the driver side, it is cheap and may be starting to fail. The actuators seem to function, since sometimes the air is hot , sometimes cold,depending on its mood.

The control module unfortunately may be starting to fail, which is over $100. Maybe a bad solder joint, a capacitor going bad, a microprocessor starting to fail. The temp sensors are many, so I will remove to get the part number.