Hot/Cold Climate Control

MickeyMag

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I have a new problem with my’04 Park Ave Ultra that I’ve had for 4 years (125K miles). The climate control heats up the cabin to a nice 80 degrees for the first 30 minutes of driving, ambient temp 30-40 degrees, but probably in any cold temps. Then it begins to pump in cold air through the defrost at the same time that it is heating through lower ducts. I believe this can be a desired thing, especially when there is sunlight coming in the cabin, but in my car this does not depend on sunlight and it is putting way too much cold air in through the defrost and it does not stop adding this very cold air, so that the cabin soon becomes uncomfortable in spite of the warm air coming in down below.

I took the car to the local repair shop and they reached a conclusion they admitted they weren’t too sure about: they said they thought it might be the control module in the dash, about the size of a radio, sending a signal to add some cool air, but never sending the signal to STOP sending the cold air. I also wasn’t too sure about this diagnosis, but the situation was made worse by the fact that they say they cannot buy that control module, it has to be sent back to Buick for repair, cost unknown. Interestingly, on the part they pulled from my dash they found that yellow inkpen writing like a salvage yard might use, suggesting maybe the part had been replaced before, though not during my ownership.

Then the shop said they found a “Buick LeSabre Climate Control 1623 Remanufactured” unit for sale on Amazon for $129, but even this would need to be programed (“flashed”?) by GM to work on my particular car. Again, not sure what the final cost would be…or whether it would solve the problem.

So I decided to take the car to the dealership for a diagnoses. They said they poured a diagnostic fluid in the coolant and decided the car has a very early stage head gasket leak, leading to air pockets in the cooling jacket, which results in the unwanted cold air from defrost. This does not make sense to me, not when warm air continues to come in through lower ducts. They want $2,000 to fix the head gasket.

My own sense is that this is a duct door or actuator for a door, but I don’t know which door or how to diagnose it.

I’d love to hear thoughts on this. Thanks.
 
you can test for a head gasket leak by buying a coolant hydrocarbon test kit at an auto parts store.
Have you noticed when checking the coolant level on a totally cold engine if over a period of a few days of usage that the level goes down?
Have you noticed excessive white smoke coming out the exhaust?
 
I'm guessing the dealership used such a kit for their diagnosis. Actually, I've never added coolant in the four years I've owned the car and definitely not seen excessive white smoke from tailpipe, which I would have noticed. My question is, does that diagnosis even sound plausible, that a very early head gasket leak could lead to cold air from defrost with hot air from heat duct? I say, no way. Any thoughts on the supposed connection between my climate control problem and the supposed head gskt prob? I could see a connection only if I lost heat in the cabin altogether.
 
I'm not buying the head gasket either. I think it is a malfunction in the climate control or an actuator. I'm not sure why the dealer is so sure it is a head gasket without checking anything else. I'm sure the FSM has a troubleshooting procedure for the climate control. I think it would be wise to buy one and see what it says. Wouldn't it be a bummer to spend $2k on a head gasket job and still have the same problem?
 
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I'm sure the FSM has a troubleshooting procedure for the climate control. I think it would be wise to buy one

Thanks, Cadillac Al. Okay, so pardon my out of date knowledge, but what's an FSM, and how much and where to buy?
 
I'm sure the FSM has a troubleshooting procedure for the climate control.

Okay, I figured out a FSM is a Factory Service Manual, and I'll probably see if I can pick one up later this week, but I'd sure love to hear of someone who has had a similar experience. Can't believe my park ave is alone in this climate control problem described above.
 
a control module can be programmed by a locksmith don't send it to buick i had to do it to a 2000 ford taurus cost me $80

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but it does sound like a computer problem to me
 
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