AC Question

[brodee]

I just put on a new compressor and dryer and switched to 134a in my '89. Now the compressor is cycling very quickly, like every couple of seconds. I'm guessing I need a new pressure switch that is made for the adjusted pressure of 134 instead of r12. Does anyone know where I can get one or what a part number may be?

Thanks!

[EverWiser]

Sounds to me like your pressure may be either too high or too low. I'm not sure about the E30 but I know some of the E34's had a high pressure switch in addition to the low pressure one. I'd recheck your pressures and adjust accordingly. I doubt there's a "higher" high pressure switch and I'm betting you're over on the charge causing the high side pressure to be too high thus cutting the compressor out before you cause damage. When your system was charged was it a cool day? It's easy to overcharge the system on cooler days. Just my .02.

[brodee]

Hmmm.. I'll have to check that out. Do you know where the high pressure switch is? It was definately NOT a cool day today (we don't have any of those in southern Texas). It is possible that we overcharged it though because I think spec is around 2 pounds and we put about 35 ounces in it. Do you know what pressure it should run at complete charge?

Thanks for the help.

[brodee]

Sounds to me like your pressure may be either too high or too low.

You had it. System had too much pressure in it. I bled a little off the low side and the compressor is cycling normal now.

Thanks for your help!!

[EverWiser]

Glad to hear it...I redid an ex-gf's 525i (we were in LA - Lower Alabama, damn hot there too) and accidently did the same thing. R134a runs at higher pressures than does the old R12 so it's really easy to end up a little on the high side. Congrats on fixing it. 8)