heater system problems, please help !!!!

[patallen]

My 1992 325i blows only hot air.

The control is the one with 2 knobs for left and right temp, with 2 other larger knobs for the fan speed and vents position. All the rest seems ok, sped,...it only blow super hot air, no matter how the temp knobs are positioned. I also try the AC, the compressor turns on, but it still blows hot air.

I am thinking about a sticking control valve, where is it located? near the firewall, at the head?
The heater control ecu have been replaced by po at the stealer. I have opened it (i am electronic guru), nothing burned at first sight.

There is also a slight smell of coolant from inside the car (i guess the heater core is leaking, to top it all).

Is there some kind of hiden feature that if the outside temp is below xx degress, that the heater will always blow "some" hot air no matter if i turn it to max cold??

thanks for any inputs

Pat Allen

[tophermack]

bad temp sensor maybe???

[patallen]

Originally Posted by tophermack

bad temp sensor maybe???

you mean the ones into the heating system, right behind the center cluster?
maybe...i can check them easely, they are only thermistors.
How can they fail anyway, i dont think they can...

thanks

Pat Allen

[tophermack]

ya the sensor thats on the control unit on the lower right hand side. i dunno if it can go bad or weather it defaults to heat if it does... just brain storming.

[patallen]

I have the schematic in front of me. What hits me is there is a dedicated temp sensor for the outside. It is not the one that is in a brake duct. So where is this one??
anyway. I will check their resistances, they can be checked very easely.
I will also check the dual valve solenoids, it look like it can be opened by driling the rivets. i can only think about air lock in there, and some accumulation of limestone or white deposits that will make the valve stuck in one position...

I will also check the proper operation of the knobs.

Pat Allen