ZEUS+

When servicing an ac system , it is best for entire system to be functioning properly. The system can be filled to correct charge weight even if rear is inop. If it works, charge system with it on. The expansion valve(s) control the proper amount of refrigerant needed to properly cool evaporator. This is determined by evaporator outlet temperature and pressure balance in valve. If not enough refrigerant is flowing to cool the evaporator valve will open more or vice versa.

Tony

Thanks. I had it recharged with the rear air on as well.
When it was initially hooked up it , the gauges read 100 on the high and 10 on the low Defintiely not good for the summer months to come and why it was performing marginally at best. My records show that the last time it was serviced was 1998 with 110k on it....it now has 160K. So i guess 50k miles and 9yrs isnt too bad?
The high side was brought up to 200 and the low side drew nicely down to 29. The air coming out even at idle was cooler than it ever has been.


thanks for this link also...
https://www.928gt.com/t-wallyhvac.aspx
A MUST read now summer is upon us. Im sure there will be rash of AC questions/problms etc etc in the next few months.

Bill Ball

I did not know this. All of my new cars have held a charge for the entire time I owned them. Our 99 Durango's AC, for example, is still going strong after 8 years. Same with the Caravan we had for 10 years prior to that. So, I've always thought that anything less was unacceptable.

The rebuilt compressor in my 89 has a leak at the front seal. It's still blowing cold after almost 2 years, so the leak is quite slow, but there is an oil drip stain there and my sniffer goes bezerk in that area. The old compressor was tight (no leaks) before it seized.

Anyway, I've never considered any leaks that I can find with the sniffer to be acceptable and I won't charge a car that has a detectable leak because there is no way for me to know how bad it is (is there?) but I'm just an untrained amateur with a bunch of AC tools, so I'm listening.

ZEUS+

R12 systems are able to perform well with minor leaks due to the larger capacity. You are lucky with your vehicles. Chrysler has a very high failure rate. Mobile ac has been a leaker since day one. It's just the nature of the beast residing in a hostile enviroment.
No disrespect Bill, but tools and novice experience is a little different from what is experienced everyday as a profession. I have built decks and a doghouse. My construction buddies have experienced more than I ever will..
Technology has changed dramatically, the common leaks have not. Oil, air, fuel, refrigerant etc. leak.
http://72.14.209.104/search?q=cache:...nk&cd=14&gl=us Page 4
http://www.nrdc.org/globalWarming/crh0904.pdf Page 26
http://www.aa1car.com/library/ac98.htm

Fogey1

Zeus, did I read recently that some mobile systems are moving to electrical power (rather than a belt), eliminating the shaft leak?

ZEUS+

I'm sure they are already developed and waiting. I read about hybrids having both. Due to the stop and go, the electric unit will kick in when the belt driven unit stops. This is all interesting, but should really be in an ac forum.

cfc928gt

I renewed my '89 A/C system last year, all new O-rings, new dryer and I rebuilt my compressor. It wasn't leaking but I thought it would be a 'good idea'.
The front seal kit, which is supposed to be for either R12 or 134a, was a bit different than what I pulled out of the unit, which of course in '89 would have just been for R12. I now also have a drip just like you describe. Ticks me off to no end, how can you judge how much oil you've lost since they only hold about 4 or 5 oz IIRC. R12 is definately going up in price, at least on ebay.

ZEUS+

Depends on compressor. Can be as much as 12oz.

cfc928gt

Zeus, thanks for posting that. I put back in what I took out plus a couple oz more. I guess I should have left well enough alone and not rebuilt the compressor since it's definately not sealed like it was.

928 obsession

Well it looks like I encountered the exact same problem last week. I brought my '82 to an ac shop and they evacuated and filled the system. However as with you they filled it at the high pressure port instead of the low pressure port. The assumed low pressure side was high while the high pressure was low, but in essence it was completely reversed. They recommended I replace the compressor and expansion valve and bring it back. Thankfully I just replaced all o-rings, the expansion valve and the receiver/drier and I was about to buy a new compressor until I read this post. I'm bringing the car back tomorrow to resolve the problem and hopefully have my ac blow cold again. Thanks for the post you might have just saved me some $$$$$.

dprantl

How could anyone that claims to be a professional with refrigerant systems mistake a high-side connection for a low side? It has absolutely nothing to do with what car it is (or a house, for that matter), if the port is sticking out of the drier, it is 100% a high-side port. I would not go back there. Or... did they purposely charge using the high-side, because that is one valid way to charge the system.

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

928 obsession

I really do not know, but I'm am going back tomorrow to have a few words with the owner. I completely agree that if they advertise as being professional they should have not made such a error.

dr bob

I think they are trying to bull-wink you.

Important questions for me would be along the lines of "is there any left in the system?" Having a low-side fill system attached to the high side offers the possibility of your compressor pumping your refrigerant right back into their system, if any made it in at all. With nothing or very little left in your system, it would have the symptoms of inadequate compressor function. Sooo.... Figure out how to get your money back, after you take it to someone who knows what they are doing. As Dan points out, there's no way to do any diagnosis or a valid fill without the lines connected to both sides of the gauge manifold set.

Good luck in your quest!

928 obsession

They had both sides connected to the gauge set when they added the freon. The high side where they vacuumed and pumped the freon into read around 120 psi after filling the system while the low side read around 0 psi with the compressor running. Would those readings be related to the improper filling on the high side? After they felt the compressor was bad they evacuated the system from the high side. I really wish I had researched more on ac before I brought it to the shop, but I felt they should have known what they were doing.

blown 87

Unless of course it is a accumulator/drier system which is always on the low side, like so many millions of cars running up and down the road.

If it is a receiver/drier system then it goes in on the high side like our 928's.