Niels67

Hi,

I am restoring my 1972 Cutlass A/C and was converting it to 134A. After I had all back in place together it appears that the Ambient Switch in the evaporator housing does not properly cut off power to the compressor clutch when the temparature in the air stream reaches aprox. 32°F ~ 0° C. with A/C running well. I had tested it by placing it in the freezer near the steaks and had a continuity check where it clicked and had continuity after a while blowing ambient air on it. So does it wear out and changes switch temperatures ? Here is my question. Does anyone know how it is possible to check or even recondition the tin metal type ambient switches by cleaning or how can I open them ? Is it a simple Bi Metal in there ?

Another problem is the thermal limiter fuse which appears to be blown an which is not available here in Germany. Can I just solder the broken connection betwee the center contact and the left connector of the fuse or how can I test it if it is working.

Third question is, is there a disadventage leaving the Super Heat Switch connector off in the back of the compressor. I am afraid it is had to find a new super heat switch if it should blow for some reason.

Thanks, Niels

matt69olds

If I remember correctly the superheat switch is just a fancy name for a high pressure cutoff switch. I think it’s only use is to shut off the compressor if high side pressure goes to high. I’m pretty sure your car uses a POA valve, I’m guessing it’s not calibrated for the different temp and pressure readings of 134a. I’m sure it can be done, I have seen many cars with functional ac using a POA valve

Fun71

I thought the same when I read this post earlier today, but I know there are differences between 71nd 72 and thought, well maybe there is a temp cutoff switch. But why would it also have a POA valve like the earlier cars? The POA valve (also called suction throttling valve) regulates the flow of refrigerant through the evaporator to maintain the temperature right about the freeze-up point. Makes no sense to me that there would also be a compressor cutoff switch, but then as I said, I don't know what is different about a 72 vs the earlier cars.

Anyway, as matt posted, the POA valve should be calibrated for R134A pressure in order for the system to operate properly.

These posts have good info on the subject:

https://classicoldsmobile.com/forums...2-cutlass.html

https://classicoldsmobile.com/forums...libration.html

Niels67

Well, thanks for the hint about the adjustment of the POA valve, will try that and see how to get the pressure reading as close to what the guys wrote in the other post. Great many thanks for the advise.