A/C cooling

[Mcguyver2]

I have several issues with the A/c on my 85 528.
First I seemed unable to stop the outside from leaking into cabin. real bad during winter cold air blows in through a/c console grates.
Now the summer problem is that A/C blows cold for about 45 min then appears to freeze up. Let it stand or continue driving in off postion for about 30 minutes then it's ok for the next 45 or so, bummer here in the south. The system is still on R-12 and according to guages fully charged. Is there a thermister probe that cycles clutch?
Next if you put your hand down next to fire wall at heater core its hot. I would think heater valve in coldest postion core should be at least cool. Combine all this and pitiful cooling, right.

 

[dhf30]

Sorry, no help here.
I have similar problem on 90 525i.
Mechanic found leak and replaced evacuator valve. When I picked up car, A/C was always on an blowing ice cubes and condensation from vent. Back to mechanic and they removed/replaced relay switch and compressor clutch activated correctly. Now, with system fully charged and no leaks, minor cooling lasts 5 minutes and cycles to warm air. Shut off A/C for several minutes (10 -15) and then same thing...cool air then cycles to warm. Mechanic thinks it is electrical due to many temp sensors (cabin, evac valve, etc). What is causing this problem?

 

[Montana]

Here's a possibility:

AC's will freeze up if there is not enough volume of air going through when they actually work TOO well. One suggestion...keep your air recirculation switched OFF. This way the AC is constantly drawing warmer outside air. This, in effect, "melts" and prevents the freeze up but it is still cold enough to cool the interior. And/or use a higher fan speed (from startup) to increase air volume through the coils. You may also want to investigate any blockage to air flow due to debris thus causing the same low-volume freeze up.

You will find this more common on the highway since the AC runs more efficient and cold then. You're cruising on the highway, fan on lowest setting, and whamo -- freeze up and it gets warm. That's why when you wait, the unit thaws and can operate normally again.

 

[Montana]

Also, switch your AC off the AUTO setting and manually switch to dash vents only. My AC in AUTO would be cold up top but for whatever reason (even set at 60 degrees), would crank hot air up at the winsheild and under the seat at the same time thus competing with the cold. Not using the AUTO solved that problem 100%.

Good luck.