Porsche 944 Air Conditioning

7-3-2005

Mounting Bolt for AC compressor, rear: 13mm
Mounting Bolt for AC compressor, front: 17mm
Hose attachment bolt at AC compressor: 13mm
Bolts on A/C Dryer: 19mm

Oil for Nippondenso 10P15E: 46 PAG
AC compressor o-ring diameter: 16mm, and something smaller.

Associated Parts (Amazon Links)

Comments

PAG is short for polyalkylene glycol. PAG-46 is recommended for the stock ac compressor. It does not mix with the mineral oil used in R-12 systems, so all the old oil must be cleaned out.

There is also POE (polyol ester) which is supposedly less incompatible with mineral oil and is compatible with PAG oil.

Porsche Service Bulletin for 944/951 A/C Retrofit

According to the service bulletin, system capacity is 130+-20ml of oil and 860g of R134A.
860g = 1.896lb = 30oz., 130ml = 4.4 fluid-oz

Tools Needed

Gauge set
Vacuum pump
Can tapper

A few notes

If you put a R-134A adapter on the low side fitting, you will not be able to plug the R-134A coupler on it! The adapter (just barely) fits, but there is not enough clearance for the hose coupler to pop on. I had to unbolt the ac compressor and slide it down to get off the connector.

Get a R12 hose set! There's no reason to change the fittings--you can fill it with R-134A thru the R12 style schrader valves.

If you want to ignore my advice and get an adapter, Amazon has a right-angle adapter. I have no idea if it will work on the 944 compressor.

Right angle adapter

Porsche 944 Air Conditioning Part II

6-10-2006

The air conditioning held out for 2005, but would not cool any more for 2006.

Filling it with the R-134A adapter attached was just not possible. So, I had to remove the low-side adapter on the ac compressor and start all over again. In order to get access to the adapter I had to remove the hoses from the ac compressor.

The routine goes like this:

Evacuate

Hookup gauge set to high side, low side, and vacuum pump.
Open valves and run vacuum pump for 30 minutes, to boil off all moisture.
Close valves and make sure vacuum is held. If not, there is a leak.

Fill

Jumper low-pressure cutoff switch (next to left headlight)
Hook up R134 can to hoses (purge air from line)
This is a good time to add oil, if needed. Pour some in the hose, the R134 will push it into the system.
Open high-side (red) valve. This will let some of the R134 go into the system.
Once you've got as much as will go in there (putting the can in warm water helps), close the high-side valve.
This is very important. If you don't close the high-side valve before you start the car, the can might burst. That would be bad.
Start the car and press the a/c switch.
Open the low-side valve (the one going to the ac compressor) and let it suck in the R134. Suck suck suck.

Porsche 944 Air Conditioning Part IIIa
7-15-2010

The A/C just turned off while driving.

Pressure seems good, the compressor clutch engages when jumpered to 12V. But the compressor is not getting 12V when the A/C is turned on.

The shop manual suggests troubleshooting from the low-pressure cutoff switch on back, which makes sense.

Here is the troubleshooting directions from the shop manual:

Check for 12V at compressor.

Yes - replace clutch

No - check low-pressure switch

Check voltage at low-pressure switch

Voltage at only one connector--system has low pressure or switch is defective.

Check A/C relay

Now at this point the manual starts talking about term.3 and term.2, but on my relay, we only have terminals 30,31,85,86,87a.

Check de-icing switch.

There is a switch that is supposed to turn off the compressor if it detects that the coils in the passenger compartment are icing up.

Voltage at only one pin, defective, replace

And the final choice is:

Replace Control Switch

Porsche 944 Air Conditioning Part IIIb
7-16-2010

At the beginning of the troubleshooting instructions Porsche should specify "if nothing on your climate control unit works (except for the fan) then that just might be the problem, dude.'

If Porsche had specified that it would have save me a lot of trouble dicking around with my gauge set and voltmeter.

I jumpered inside the fuse box from the 12V source for the fog light relay to the A/C relay output. You have to pull the two relays, so you disable the fog lights, and also you bypass the condenser-freeze switch.

That makes the compressor run whenever the car is running. A quick solution until I find out what is going on with my climate control unit.

Porsche 944 Air Conditioning Part IIIc
Also 7-16-2010

It was the damn fuse! Fuse #17, labeled 'Heating'. 7.5A

Unfortunately, replacing the fuse with another 7.5A fuse let to it blowing again. So I bumped it up to 10A. Still no good.

Note that all the current flows through the climate control unit and the snowflake switch, and burning out the climate control unit is something I'd like to avoid.

I stuck in a 15A circuit breaker type fuse. I get about 20 minutes of A/C before the circuit breaker trips. After a while, it resets automatically.

I will be replacing the compressor soon. Also the expansion valve.

Porsche 944 Air Compresser A/C

Exploded view of Porsche Compressor. I had an old one laying around, so I exploded it. Those five things on the left are tiny little double-pistons. The things that look like ball-bearings are half-bearings.

Only one section of the compressor is shown, there are two, with a back plate and nose cone.