Motosport

I have some aircon issues I'd like a little help with if possible...

My car is an '89 TS with some 90k miles on it. A year and half ago I had my aircon converted to R134 and it has been working fine since. Well, until this week at least, but as I haven't used the aircon for a couple of months, I'm not exactly sure when it stopped working.

Anyway, when I activate the aircon button it illuminates and I can hear the compressor turning on, or at least the revs drops so I guess it turns on, but no cold air at all. When I looked into the sighting glass on the drier, there was no liquid to be seen. So I took the car to a shop and had them charge the system as it was completely empty. The guy in the workshop haven't seen a 944 engine bay before though, and could only find the low pressure filler nozzle but no high pressure one. So he figured that because of the cars age, there is only a low pressure filler nozzle. I don't know much about our cars A/C system, so couldn't really guide him. So he charges the system, but it still doesn't make any cold air at all and there is no liquid to be seen in the drier. The compressor is making some grinding noises though, and the shop guy concludes that the compressor is shot and needs replacing, and that's the reason there's no circulation in the system what so ever.

When I came home I did some reading on Clarks Garage to enlighten myself, but didn't really find an answer to my questions.

So from the above description, do you guys agree on my shop guy's verdict.? And does our cars only have a low pressure filler nozzle or is the high pressure one just hidden somewhere..?

And do anyone happen to have a part no for the Denso compressor..? I'll look into where I can find the cheapest one here in Europe, as I would have to sell my house to buy a new one from Porsche here in DK... Auch...

Thanks in advance guys...

jlturpin

Usually the high pressure is on top of the compressor. But I have seen several different configurations over the years. If the clutch on the compressor is engaging, there should not be any grinding noise for normal operation. It could be the clutch grinding because compressor is locked up. You shoud be able to turn the compressor by hand without much resistance.

Alan 91 C2

Just replaced a/c compressor symptoms like yours

Motosport

Alan, did your new compressor solve the problem then..?

Alan 91 C2

The higher rpm these engines turn is a problem for long compressor life.

Yes, the new compressor has me cool again. There are several sites selling rebuilt compressors $270-400. You will want to top up the refrigerant annually. The rapid cycling of the comp clutch at high rpm destroys the compressor when low on refrigerant.

griffiths

? ? ?

The stock Denso compressor as well as the Kuehl have no issues at 'high rpms'. These units have been running on 924s,944,951 for eons. The more common issues that affect (effect) compressor life are: excessive high side pressures or lack of oil flow (low refrigerant levels); constant 'topping off' without adding oil. Add to the problem a compressor with 100k+ miles on it, they were not designed to last that long, some may but most don't.

Most systems do not have to be 'topped off' annually, if they do then obviously you have a severe leak, so fix the leak.

Rapid cycling is not normal and wears out the clutch whether its at low or high rpms.

Motosport

Sounds like a new compressor would be a good place to start... Thanks for all your replies...

schip43

Did you convert to R134? And I did not think 6800 rpm was high rpm...though mine is chipped and cuts out at 7200 but the collective wisdom was that I better quit doing that so I **** at 6500.

89 TS chipped and stuff!

Alan 91 C2

The operative wording here is low freon charge and high rpm create failure condition.

The safe plan is to observe the freon charge annually. Just like we check engine oil level periodically.

Sure, the compressors will run high rpm. But will last longer with proper refrigerant charge and lower total exposure to high speed runs at 90 MPH for hours.

schip43

Non issue!

Where in america are you gonna run 90 mph for hours! If my boost gauge hits 18 lbs my next glance is at my V1!

Alan 91 C2

Texas, 4 hours at 90. Speed limit 80, safe 88-90. Was 105 degrees F.

Found two of the discharge reed valves in the high pressure line. Compressor had 30k miles. Engine rpm at 3600+

Motosport

I still haven't found the answer to whether our cars only have the low pressure side filler valve, which is easily visible near the brake booster, or if there is also a high pressure side filler valve somewhere..??? My shop guy seems to think there's not, but reading through Clarks Garage on the subject makes me think there might be...???

Can someone shed some light on this..?

Thanks..

joker2cv

The high pressure filler valve is near the top of a/c compressor

Alan 91 C2

The high pressure port (valve) is adjacent to the shock tower, visable under the hood. The low pressure suction port is accessed under the car on the side of the compressor. I have no idea why the Porsche engineers would make access so difficult.

divil

Yes this is how it is on my '89 Turbo. Low pressure port is on the compressor, on the left side of the compressor (from driver's pov), and is pointing downwards. High pressure port on the line near the strut tower.

It is different on the early cars as far as I know but I'd be very surprised if the 89s are not all the same.