DanielD

I'm on the verge of taking the dive on a 1990 928 S4/GT...

There is one issue with the car I am concerned about, the A/C compressor clutch is not engaging after the R134 has been charged.
I know this can be one of several things running from a switch/wiring problem, clutch problem or compressor problem.

My question, of course, is this: what is the most likely culprit in this scenario? Is the compressor prone to failure, the clutch or the wiring? This could run from little or nothing but some troubleshooting time to $600 for a rebuilt compressor. Help!!!

wcj928

I just purchased a rebuilt compressor for my 91 gt from this place in Daytona Beach, FL. My mechanic was impressed with the quality of the rebuild. So far so good. www.a-aironline.com Remanufactured Nippondenso 6E171 Compressor $365.00 No core required.

DanielD

Thanks for the info.

ROG100

Porsche factory rebuilds are only $475 plus a $200 core charge.

blitz928

Kuehl conversion might be a viable option, $699, gets you the whole kit, New compressor, drier, seals, high pressure hose, oil etc.

http://www.griffiths.com/porsche/ac/...ml#Compressors

dprantl

Your '91 originally came with a Nippondenso 10PA20C. Changing to the older 6E171 also means you have to change both hoses since the compressors have the hose connections in slightly different places. Did you also swap to older compressor hoses? And... you would also have to have the older A/C belt tensioner bracket.

The easiest way to rule out mechanical issues with the compressor and clutch is to apply 12 volts directly to the compressor clutch wire (it runs down the front of the engine to the compressor just a little to the passenger side) with the car running and the blower fan on speed 2. Check vent temps, then jumper the compressor for 10 seconds, NOT MORE and check vent temps again. If compressor clutch engages and vent temps drop, the system has charge and the compressor is working.

Dan
'91 928GT S/C 475hp/460lb.ft

wcj928

Dan, I have the 10PA20C on my car as the change over from the 6E171 occurred in 1991 from what I can determine. The 1990 car should use the 6E171 that is why I referenced it for DanielD.

Niles

On my 87, the compressor did not work even though fully charged. I checked voltage at the pressure switch in front of the condensor and I had 12 volts with connector unplugged and A/C switch on. The low pressure switch was closed and had no resistance - so it appeared to be fine. Everytime I turned on the A/C, the voltage dropped to less than one volt with all of the wiring connected. The cause was a bad relay that is soldered on the A/C/heater control board, and it's a common problem. There is a fix for removing the old relay and soldering the new relay in - Thanks Dr. Bob. It's cheap and relatively easy. My money's on the relay, but you should also check the temperature switch under the cowl and the pressure switch. For getting the best price and planning for the worst, assume it's the compressor.

SeanR

Make sure you have voltage at the freeze switch first, if there is no power there you have a head unit problem. If you have power there, then jump the low pressure switch and see if the compressor engages. If it won't, next step is to test the compressor. Pull the plug that powers it from the front of the engine, jump it to the jump post. Just tap it there a couple of times. If you don't hear the clutch engage then the compressor is shot.

Rob Edwards

Both 928Intl and 928 Specialists list the 6E171 as for 80-89 cars, though I have seen other places on the web that list it for 80-90 cars. FWIW, my '90 GT has a 10PA20C on it (and the mounting bracket and hoses that are specific to the 10PA20C). It's certainly possible that the '90 you're looking at has a 6E171 on it, I would just make sure which compressor and hoses you have before you go buying any parts.

rahulsingh

Hi... Does anyone here has information about the 928 GTS AC compressor & air


pump mounting bracket... I am having a bit trouble in installation as I don't have idea about their location & number..how many of such brackets are there in car


as per the digram 1&2, there are two seprate brackets... But how to install them ...

Thanks

Tony

Bracket ends (bolt 9) go here...very easy to over tighten and strip also.

928cs

The first diagram shows the air pump system for a car without catalytic converter.
It doesn't apply to a car with a catalytic converter, like your GTS (except if it is one of the very limited number of GTSs without).

rahulsingh

You are absolutely correct about the system, but this system(above pic) is applicable for my GTS & it is rare...

rahulsingh

Thanks for the quick reply.. I am not sure if both the brackets (AC & pump) will go from the marked location.. do you remember if both the brackets are same or different, their part no. is same...