Please advise on A/C conversion

[Roa, Greg]

Dave,
I don't know if you get any of my messages, as I've never received a reply to any I have sent you, but are you sure that your compressor is working properly?

Something isn't right with your system, if it is still taking ten minutes to get vent temperatures of 60 degrees.  I converted my 4kq, which has an identical system.  I replaced the receiver/dryer, all of the seals on the compressor, o-rings, the expansion valve, and the condenser with a used one (My condenser was re-installed incorrectly by a PO, and smacked a hole in itself against the engine block, hence the replacement--thanks for the used one Elliot!).  Total cost was about $110 for the conversion, but I did my own work.

Upon starting to charge, I found that my compressor was quite weak.  I have a high side pressure that only gets to 160psi max, and low side that never drops below 80-90 psi.  Even with this weak of a compressor, I get:
Vent temps of 60 deg in ~1.5-2 minutes
Vent temps of ~55 in less than 5 minutes
Vent temps will go down to 47deg after about 10 minutes, and hold between 47 and 49 degrees.

This is in 90-95 degree weather, with very high humidity, no pusher fan, and chewed up cardboard air guides around the radiator/condenser stack.  I'm going to replace the compressor with a rebuilt one before next summer, but it'll do for now.

My point is this:  The York compressor is not the greatest design.  It hogs a lot of power, and it can be noisy sometimes.  BUT, it is fine for 134a.  It has plenty of capacity for our cars, and is still sold in the exact same form as it was in 1986 when my car was new, for use in semi trucks, with 134a.
The main thing that has been upgraded for 134a use, is the condenser.  Typically, newer cars have a larger, more efficient condenser.

Did you get numbers for your high and low side pressures when your conversion was finished, Dave?

Greg Roa
Cincinnati, OH
86' 4kcsq
93' 90 CS
83' 944


>Subject: RE: Please advise on A/C conversion
>Date: Thu, 18 Jul 2002 11:44:14 -0400
>From: <David.Ullrich at ferguson.com>
>To: <zsolt1 at telusplanet.net>, <quattro at audifans.com>
>
>First you have to decide whether you can live with an AC system that will n=
>ever cool quite as well as it did with R12. Audi does not recommend convert=
>ing any car with the York Type compressor with good reason (some other comp=
>ressors can be converted easier, but I have not BTDT with any of those). I =
>had mine converted and it's been a nightmare, but worked out in the end. On=
> R12, from what I've heard, you should be getting vent temps in the lower 4=
>0s if the system is working properly. The best I can get out of my R134a sy=
>stem is the upper 40s and lower 50s (usually pegs right at 50, but varies a=
> bit). Plus it takes a LONG time to get there, 10+ minutes for so on a hot =
>day when interior temps start high. An example would be yesterday when I le=
>ft work. I hopped in the car and the vent thermometer (I just keep it in th=
>ere) was showing 120 degrees. It took 10 minutes for so for the vent temps =
>to drop to 60 on #3 blower setting (takes even longer on high). It hit 50 d=
>egrees within another 5 minutes or so. But when it's 95 degrees out with hi=
>gh humidity, even 60 degree vent temps feel pretty good! So, do you think y=
>ou could live with a slightly less efficient system?
>
>Now, onto the worst part, the conversion. First, if you are going to do thi=
>s, do it right. That means replacing: service fittings, dryer, all o-rings/=
>seals, and the expansion valve. Then flush everything (have to remove the c=
>ompressor to flush it). Now evacuate for a minimum of 4 hours and make sure=
> it will hold a vacuum, now refill with ESTER oil  and fresh R134a (ester i=
>s R12 & 134a compatible and it is a good conditioner of seals and o-rings) =
>and keep you fingers crossed. One thing to keep in mind, R134a molecules ar=
>e much smaller than R12 and will find even the tiniest ways to leak out. So=
> if your hoses are even marginal, those will have to be replaced too. Doing=
> a R12 to R134a conversion properly is pretty expensive.  My conversion inc=
>luding a new high pressure flex hose and all the things above was over $700=
>. Others may tell you to just go to your FLAPS and buy the $35 conversion k=
>it. Sure, it might work, but from what I've experienced, it won't work well=
> or it won't work very long. One other thing, make sure your radiator fan i=
>s healthy (works on all speeds if multi-speed and pulls well). It would als=
>o help to put a pusher fan in front of the AC condenser to added air-flow o=
>ver it.
>
>Overall, I guess I'm satisfied with the results. It works adequately and wi=
>ll make future recharges dirt cheap when compared to R12.
>
>Well, sorry for the novel, but HTH, YMMV. Good luck.
>
>Dave
>
>Too Many Toys:
>2002 VW Jetta GLS 1.8T Tiptronic
>1993 RX-7 R1
>1987.5 Audi Coupe GT "Special Build" 2.3
>1985 Chevy Impala Interceptor