SecaBlue

I have been searching the historic threads here and 'other' places, but cannot find the info I am looking for.

Situation is this: last year I bought my 1990 S2 which the previous owner says they had the A/C system serviced and re-gassed prior to me taking delivery. Upon delivery I drove it 700km back home, and the A/C worked flawlessly all the way, as well as through the remainder of the Summer. Then the car was parked up over the Winter and now I am driving it again, there is no A/C.

The snowflake button on the dash works with a click and lights up, and the climate control dial works with the 'click' midway to activate/deactivate the heater. I have checked the small fuse in the fuse box, which is fine (also verified by the heater function also still working), but the relay there has no sound. So I bought a new relay and still no action there or any activation of the compressor.

I would have thought that an electrical issue between the compressor and the relay would either blow the relay or the fuse... but neither.

Do I remember reading correctly that there may be another small relay behind the climate control panel in the dash?

Would the gas leaking out somewhere over the Winter cause the compressor to not activate the main relay?

I'm learning much about this car (and general mechanics) on the fly, so any feedback/assistance on where I start to troubleshoot would be greatly appreciated!

Thanks

thomasmryan

the pressure switch at the dryer is usually off-on-off. the compressor will not turn on with low gas.

PaulD_944S2

Honestly, it's not unusual for sellers to load refrigerant into a leaky HVAC system in order to facilitate a sale. Unfortunately, the next owner finds that he has some work to do. Here's some learning material:

https://griffiths.com/porsche/air-conditioning/

This is a good read for all HVAC systems even though it talks about an upgrade on 911:
https://griffiths.com/mr-ice-project/

divil

Are you sure about that? I'm pretty sure I've seen mine running with very low gas when I hooked up a gauge, although it was a few years ago. I think it was switching on and off faster than usual.

In any case, wouldn't the compressor have to turn on before it's possible to detect low gas?

thomasmryan

The switch or switches, some have 2, are usually marked with their pressure set points.

Jfrahm

Yes, I had a slow leak for years and the low-pressure cutoff would prevent the compressor from engaging when it was low enough on charge. It does not take much charge to get it to engage, you can charge into the system without the compressor running for a bit and it'll soon start. It will also "bounce" off the low pressure cutoff when the charge is kinda low where the compressor will cycle off when the suction side is low enough and then start again when the high side equalizes.

I finally found my pinhole leak on the condenser between some fins. AC leak detection dye finally did the trick but the staining was very light. It could be the seller knew it had a slow leak or (like me) thought it was fixed a few times with new O rings, new valve cores, etc. It took months for my system to leak down.