I have been driving my car with intense heat pumping into the cabin this weekend. My engine kicked the bucket and I had a service station put a different engine in the car last week. I got the car back the other day and the temp display flashes on the ECC indicating there is a fault. The air conditioning blows out warm air but the heater seems to work fine. The problem is I took a road trip this weekend and had the ECC off with the windows down but heat was pouring into the car through the floor vents. When the car is stopped and idling there is no heat but the faster the car goes the more forcefully the air enters the car. On a side note, when I first got the car back it looked like the AC compressor clutch plate was having trouble engaging but it I think it is engaging now. Any ideas what could have gone wrong? I am taking the car back in the morning but would like a few ideas when I talk with them. Thanks!

its your air mix actuator. do a search here for it and you will find that its a common problem and can be fixed by you or a service shop.

also read this when you have time:

http://trialsnuts.com/ecc.pdf

I finally got the mechanic to look at the car and he also thought it was the air mix actuator but he said it is a coincidence it stopped working after they replaced the engine. Is there any way replacing an engine could cause the actuator to stop working? When I got the car back the first time I noticed my glove box was rearranged like they took stuff out of it but I don't see why they would need to remove the golve box and work around the actuator to install an engine. If it is something they did I would like them to fix it. They want to charge $350 to do the work. Any ideas?

here is the thing with air mix actuators...........

GM used weak plastic for the gear inside of it. Over time the plastic gets brittle and then it splits down the middle, causing problems as you described.

So when the battery is disconnected for any reason.......when you got a new motor put in by the mechanic....the ACC system loses the air mix memory/position. When the battery is reconnected.....when your mechanic hooked it back up sometime after the motor install... the system does a full air mix sweep to regain the proper position.

The gear inside the actuator brakes sometimes because when the lose of power happens, the blend door that is connected to the air mix actuator does not properly stop...thus it fights the air mix actuator and binds causing the gear inside to break.

To prevent this from happening it is always good to physically turn off the ACC system before disconnecting the battery. This way the ACC system will properly stop where it is supposed to.

Yeah it would be great to pin this problem on the mechanic! But to actually prove it was directly his fault would be very difficult.

Unfortunately I would have to agree with him that it was just a coincidence that it stopped working.

That link I gave you tells you all you need to know to replace it yourself and save you the cost of having your mechanic do it for you. unless you don't want to mess with it than its worth what he is asking than.

That makes sense. Thanks for your help!

NP

Let us know how things work out for ya.....

Well I took the plunge and started the process of replacing the actuator. Unfortunately as I was disconnecting the vacuum lines from the HVAC programmer two of the nipples broke off. I saw some references to bypassing the connector but I can't find clear instructions to do this. Anyone know if there are directions to do this?


FYI- I did remove the actuator and it was broke.

i am starting to have this same exact problem