75ohm

I believe I know what the issue is, but I challenge you to draw to or refute my conclusion (which remains silent until posts go up)!

Scenario:

Late NA 134a AC system working as it was the day I bought it. Decided it was time to replace the pressure switch since the tab broke off it a while back. Purged the system, changed the receiver/dryer ensuring the IN was correctly oriented.

Lines still had R12 fittings but had the Sanden r134 conversion compressor. Added the adapter on the high-side line port. This one is just the adapter without the valve. Replaced the valve for good measure.

Compressor low-side can take an adapter but then with the swaybar mount, I can't get the gauge line or charging line on the adapter. No worries, I bought a 90-degree adapter from NAPA. Due to the angle, I couldn't get the valve tool on the port so I pulled the valve out of the 90-degree adapter and pressed on.

Got the gauges hooked up, drew a 15 minute vac and checked for leaks. No leaks. Broke the vac, removed the high port valve and poured 1 ounce of medium viscosity PAG oil in the high line for the new receiver/dryer. Drew vac again for 30 minutes and held 26Hg. On goes can one of 134a. It takes it decently and the system is blowing “cool”, not cold. Expected, as the sight glass shows bubbles. No worries, can two going in, but won’t take it readily and system still blows “cool”. Here’s where it gets interesting…

Houston, we’ve had a problem.

Low side gauge is at 80, high side at 125.

Given the scenario… what say you?

-75ohm.

potent951turbo

Is this one of those aftermarket kits that require the special brackets to mount the compressor to the 944 A/C bracket?

75ohm

Not that I'm aware of...

potent951turbo

I asked because we had an aftermarket kit on a previous 951, and the design was terrible and put the valve right up against the sway bar frame area making it impossible to get the freon hose connected. It also used brackets that bolted to the compressor to adapt it to the 944 mount, and the brackets started cracking after a few months. A nightmare to say the least.

xsboost90

hmmm...did the compressor have oil in it already? the 134a will have some oil in it as well-wonder if there is too much oil? 80 is really high, is the compressor kicking on? maybe its off on the high pressure switch and not drawing it in so the gauge is reading high?

75ohm

Perhaps the same one. It's a Sanden compressor. Hence my purchase of a 90-degree adapter. When I got the car I noticed the compressor tab rubbing the sway bay, heck with that... cut if off.

75ohm

Same compressor.
New receiver/dryer.
Added 1 ounce of oil to the high line to draw into receiver/dryer.
New pressure switch.
Compressor clutch easily engages.

Continue!

joes

I would say first that you could have an adapter problem. I do a/c refrigeration all day and use the old type gauges on both a/c equimpment and my 944. why add adapters? If the adapters if not seated correctly they could be giving you a false reading. Check that first. Otherwise the readings that you site suggest that the system is approaching balance. ( only 60 psi differential)

1. the compressor is not pumping very well
2. the expansion valve is open too much
There are a lot of variables to consider though. I would drive it down the road for a while with the compressor running and then try it. (circulate that oil)
The cool weather could be a factor if the fans are running. (try some card board) Also increase the idle while checking checking pressures, the compressor doesn't work very well in cool weather (if it is cool there) at a low compressor speed.

75ohm

Thanks for the response... allow me a chance to make sure I get all the comments replied to...

Adapters... my guage set is 134a only. The high-side is an adapter without a valve and is properly seated. The low side is a 90 degree adapter without a valve is properly seated. New valve on high side.

Correct observation on balance. The system does stay within that PSI and eventually balances out as expected about 5 minutes after shut down.

Car was idling for about 20 minutes during all refrigerant addition, along with, increased throttle for about 5 minutes in duration. Outdoor temp was in upper 70's, low 80's while performing this maintenance.

Continue!

75ohm

Only three folks accept the challenge?

Zero10

Sounds like the wrong expansion valve. You need one with a smaller hole for R134 operation, no?
What are the pressures at 2000RPM? I see that most people on here seem to agree that the pressures are properly measured only at 2000RPM.

75ohm

Pressures remain unchanged at 2K on the tach for 5 minutes in duration.

Expansion valve has not been reviewed.

whalebird

+1 JOES. Compressor is junk if its the aformentioned kit-probably is. note the outside temp when testing, roll up windows as well. if you have one of those infrared temp readers get temps off of the condensor and somewhere around the inside of the center vents. Completely disregard the sight glass and fill system using low pressure readings only. I would say you probably have overfilled the system especially if you have added oil to an already filled system. Did the dryer have oil? oil will take up most of the space freon is supposed to be in and thus reduce its function. Should have no problem with exp. valve. Stock ones work great for 134.

75ohm

Thanks for the continued responses... keeps it interesting!

System was emptied and a new receiver added. One ounce of oil due to this.

Never got more a little more than 1 can of 134a in...

Positive news on the expansion valve... I'd sure hate to have to dig that out.

Enough suspense already, I'm pretty confident the compressor is dying. The car never did blow very cold air and I didn't think much of it because I'm usually running with the air off and the windows/sunroof open to enjoy the moment. Nonetheless, the whole thing started when I decided to add 134a. The valve got stuck and there went the 134a. Now time like the present to swap that pressure switch anyway and the receiver while I'm at it. Easy, right? Not so easy, as indicated by this thread. Compressor kicks on, but I honestly don't think it's doing much. Think the valves are shot... thus, recommendations by anyone for a compressor?

Thanks all!

F18Rep

How bout this? You filled too fast, dumping liquid into the low side (which is right on the the compressor) and now have a damaged compressor. Um, just a theory. Bruce