A/C Problem at the Receiver/Dryer

bluecat · 03-29-2006, 03:43 PM

I've enjoyed reading these posts for a long time, and now I need to ask for help with the A/C in my 77 Targa. After the R12 had been removed for the R134 retrofit, in removing the receiver/dryer the small (approx. 1/4"), male brass fitting coming into the top side of the dryer was frozen, and sheared evenly at the interface. There are two black wires that go from the fitting through the left front fender well near the "fire" wall. The fitting is about 3/4" round where the wires are molded in with apoxy, and has a 19mm wrench hex on the dryer end. The brass male fitting has a hole through it's length. I have webb- searched for it's identity and source. The dryer is configured like the one for that model in Pelican's catalog. I'm hoping that someone can identify the part and a source for it. Thanks in advance for any help.

Jim Sims · 03-29-2006, 04:16 PM

It's a pressure switch; about half the time the receiver/driers I get from NAPA have them already installed. The fitting thread is a regular v-thread that is sealed with an o-ring. Since the systems I have dealt with incorporate a pressure switch at the compressor I remove them and install a plug made from a fine thread bolt and reuse the o-ring. The usual purpose of the switch is to cut power to the compressor when the system pressure becomes too high due to lack of air flow over a condenser or other malfunction. Have you bought your replacement R/D? It may have a new switch already installed.

bluecat · 03-29-2006, 05:21 PM

Jim, thank you so much for the information. I had suspected a pressure switch, but I am profoundly ignorant about the function of some of the A/C components - as it is, I still dont know what the wires go to. From what you have told me, I can buy the part at NAPA. Thanks again!

Jim Sims · 03-29-2006, 06:23 PM

This probably looks like what you have installed; it's a low and high pressure switch: 2 bar and 20 bar cut off pressures.

http://www.pelicanparts.com/cgi-bin/smart/imgdsply.cgi?pn=95961313700-M212

PN 959-613-137-00 M212 $8.75

bluecat · 03-30-2006, 04:30 AM

Jim, thanks again for your help and the photo of the part. I'm positive that that is the correct part! Instead of the terminals at the unit, mine has the fixed expoxy connection, which I'll snip and attach the blade connectors. I went on line last night to NAPA with a request for a search for the part. Jim, I appreciate very much your help.

bluecat · 04-01-2006, 08:41 AM

Jim, I got the part from NAPA but the male fitting is too big, and it looks like an SAE thread, not fine like the metric female on the dryer. I want to get your opinion on this; what if I just plugged the dryer off with a bolt and the 'O' ring as you mentioned what you do when there was a pressure switch elsewhere? Do you think I could get away with that? What is the worst that could - blow out a line or ruin the compressor? I would appreciate your opinion. Thank you again for your help.

Jim Sims · 04-01-2006, 09:02 AM

Yes, you could plug the port with a metric bolt and o-ring or order the correct switch with metric threads from Pelican or just get a R/D from NAPA (~$30) that the switch you have in hand fits (make sure the hose fittings are correct - you appear to have an odd system for a 1977). The risk of the plug approach is over pressurizing the high side of the system; I would expect either the hose between the compressor and deck lid condenser, the deck lid condenser or the seals in the compressor to fail first in the event of a overpressure but really anything from the compressor through the expansion valve (in the evaporator/blower unit) is at risk. However for many years none of the Porsche systems had these cutout switches. It is an EPA requirement that conversions to R-134a incorporate a pressure cutout switch to reduce the likelihood of refrigerant venting to the atmosphere.

bluecat · 04-01-2006, 10:47 AM

Jim, thank you again for your help. As for getting the part from Pelican, I went to their Tech Info center earlier, and they couldn't identify the part. If I can't get a reducer, I'll plug with a bolt. Words can't adequately express my appreciation to you. THANK YOU!