Did a frame-off on my '71 El Camino. The A/C system was removed and stored with al openings taped off. It was re-installed with new compressor and dryer, then evacuated and recharged. It had already been professionally converted to 134 by the PO. It cooled great for about 2000 miles (several months) with no problems, then suddenly began blowing hot. I took the unit to a shop that does not do A/C repairs and they put more 134 in. It still blew hot but according to the technician the pressures were very high. He unhooked the compressor and suggested I take to an A/C shop.

My regular mechanic checked it and he suspected an expansion valve, although he said he was not familiar with POA valves and it could also be that. I looked up the info on testing the POA valve at autoacforum.com and took the truck to him along with this info:

http://www.autoacforum.com/messageview.cfm?catid=20&threadid=7567

He replaced the expansion valve. and using the method described on the A/C forum, he tested the POA. The original POA would not read anything on the gauges. I got a used POA from a local wrecking yard and he tested and adjusted it to 26 lbs. He was unsure that it was set right, saying that there was another line going into the evaporator that was not plugged and he did not see how you could get a correct reading. After charging with what he felt was the correct amount of 134 the unit still didn't cool and the pressures were low. He continued to add 134 until the pressures were acceptable to him (30 to 35/150 to 175) and the air coming through the vents was only slightly cool, nowhere near what it needed to be to cool the vehicle. HE also showed me that the lines were frozen up to and including the POA valve, but barely cool if at all beyond that.

Any suggestions as to what to try from here. My technician wants to eliominate the POA valve and retrofit a pressure cycling switch somehow. I would rather get it repaired as it is.

P.S. Sorry this is so long. Thanks,

Ron Griffith

http://elcaminocentral.com/gallery-album_rgriffs-71-SS-Clone.html

Old Air Products make a conversion to clutch cycling piece to replace the poa. Do the conversion and you won`t regret it unless you are looking for the 100 % stock. I`ve had 4 done and work good.

If the pressures are high, that could be a possible sign of a restriction in the system.

Old Air Products make a conversion to clutch cycling piece to replace the poa. Do the conversion and you won`t regret it unless you are looking for the 100 % stock. I`ve had 4 done and work good.

I generally swear by things from Old Air Products, but those POA eliminators are something to be avoided with OEM A6 compressors. (Most AC parts suppliers carry them, not just OAP). The clutch on the compressor is not made to cycle and will fail in fairly quick time. Aside from that they work really well. I have not found a supplier for an A6 clutch designed for a cycling clutch system. In my experience the OEM clutches work good for a while but then the plate fractures. In NE Ohio it takes about 2 "cruising seasons". The clutch often fails early in the 3rd season usually. This is assuming starting with a new\reman unit.
OAP has a compressor kit (Sanden?) to replace the A6 for Cycling Clutch applications, as do other suppliers.