Type85 AC converions to R134a

David duandcc_forums at cox.net
Mon Aug 9 16:47:03 EDT 2004

From: Ed Kellock <ekellock at gmail.com>
Date: 2004/08/09 Mon PM 02:09:59 EDT
To: David <duandcc_forums at cox.net>
Subject: Re: Somebody was looking for a CGT 2.3 auto?

Dave, the a/c compressor on my 87 CGT 2.3 went south a couple years
ago and I thought it might be a good time to convert to r143a.  Can
you tell me what was involved in doing that on your car?


First you have to decide whether you can live with an AC system that will never cool quite as well as it did with R12. Audi does not recommend converting any car with the York Type compressor with good reason (some other compressors can be converted easier, but I have not BTDT with any of those). I had mine converted and it was a nightmare, but worked out in the end. On R12, from what I've heard, you should be getting vent temps at or below 40*F if the system is working properly. I've found that if you adjust the AC thermostat you can get even lower temps. My R134a converted system eventually gets down to the mid 30s. But it takes a LONG time to get there, 10+ minutes for so on a hot day when interior temps start high. An example would a while back when I left work. I hopped in the car and the vent thermometer (I just keep it in there) was showing 120 degrees. It took 10 minutes for so for the vent temps to drop to 50 on #3 blower setting (takes even longer on high). It hit 45 degrees within another 5 minutes or so. But when it's 95 degrees out with high humidity, even 50 degree vent temps feel pretty good! So, do you think you could live with a slightly less efficient system?

Now, onto the worst part, the conversion. First, if you are going to do this, do it right. That means replacing: service fittings, dryer, all o-rings/seals, and the expansion valve. Then flush everything (have to remove the compressor 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 is R12 & 134a compatible and it is a good conditioner of seals and o-rings) and keep you fingers crossed.

Now that everything is converted, I'd consider adjusting the AC Temp Sensor. This is the sensor that controls at whjat temp the compressor custs oput. The factory setting is around 42*F. I've adjsuted mine down to 34*F and am very happy.

To adjust the temp:
Remove the glove box as an assembly and lay it on the passenger floor. The Fuel Injection computer is attached to the right side of the glove box. Leave it there because you'll want to run the engine and drive the car around.

With the glove box removed you'll be looking at the Evaporator. To the right of the evaporator is a small box, gold anadized in color, with a 14mm nut facing you to hold the box in place.

This is the temp sensor for the evaporator core. Take note of the ether filled capilary tube that comes out the top of it and goes to the left across the front of the evaporator and then into the fins of the evaporator. Break this tube and you're screwed......so proceed with caution!!!!

Undo the 14mm nut that holds the temp sensor switch in place. Lower the temp sensor and bring it and it's capilary tube outward just unit you can see and get to the top of it.

On top you'll see a philips screw. This is the temp adjuster screw. Scribe a line on it and on the housing for reference.

Turn the screw COUNTER-CLOCKWISE to lower the tempurature at which it turns off the compressor.

As I said, mine was blowing 43 degrees. 2-1/2 turns COUNTER-CLOCKWISE got me to 30 degrees.

So, make your adjustments slowly with the car sitting there running, doors and windows closed and see what you get. Take is slowly.

Once you get where you want. Go for a test drive and see what you get on the road. I noticed I had to keep turning the screw counter clockwise a bit further to get 30 on a test drive.....as compared to what it took to get 30 in the driveway.

With it torn down this far, it would be a good idea to remove and clean the evaporator drain pan.

One thing to keep in mind, R134a molecules are 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 including 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 kit. 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 is healthy (works on all speeds if multi-speed and pulls well). It would also help to put a pusher fan in front of the AC condenser to added air-flow over it.

Overall, I guess I'm satisfied with the results. It works adequately and will make future recharges dirt cheap when compared to R12.

Well, sorry for the novel, but HTH, YMMV. Good luck.


1987 Coupe GT Special Build 2.3 (H4s, custom exhaust, Borbet Type Es with Kumho tires, Recaro Trophy seats, Euro 90 Sport 3 spoke steering wheel, 4Kq swaybar, Boge TurboGas struts/shocks Kenwood Bazooka & Blaupunkt stero system, R134a converted AC blowing 34*F, 35% metalic charcoal tint, fresh paint in original Anthracite Black)

2002 VW Jetta GLS 1.8T (wife's, stock)

1993 RX7 - R1 (shared toy, stock)

1985 Chevy Impala 9C1 (fun beater and boat tow vehicle, stock police package)

1978 Impala SW (stuff hauler, restored with crate new LT1 transplant) 

All in SE VA

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