71 AC Question

[Patrick B.]

So, pretty sure the previous owner of my 71 converted it to 134A. Charge port on low side is a 134a port and pressures look closer to 134a than 12 but of course, no sticker. I just want to confirm diagnosis here (or get a couple second opinions). The car had negligible Freon so I pulled it down and she held vacuum for about an hour. I charged and started monitoring pressure - I would expect to start seeing suction and clutch cycling but not getting anything measurable. It was hot (93) here in Delaware so I was sitting around 55 on suction and 225 on high side. I charged with a little leak detect so I'll go sleuthing tomorrow.....

As a matter of fact the clutch has not cycled at all to my knowledge. The inside cabin air at idle gets to about 68 or so. If I run up the idle to 2K, she will cool down to 63 degrees out of the vents. Book says I should be able to get her down to 51. I have lots of condensate on low side and POA so thinking not expansion valve problem. This looks like original A6 so thinking she's getting tired? I was planning on cleaning condenser tomorrow but thought I'd ask the group their thoughts.....

[Jim T.]

Re: 71 AC Question

Patrick this is only an opinion. With your 1971 having the 134 type connectors installed and with the price and availability of the R12, I give my opinion answer of you having 134. I still have R12 in my 1970 and 1985 Corvettes.

[Edward J.]

Re: 71 AC Question

Pat, R134 does not have the same cooling capabilities as R12 and pressure will be higher on the low and high sides gauges,hotter outside temp will also cause higher pressures. I have done many conversions in my time and thetr is one thing you should be doing when charging the system- is subtract some Freon form what the factory tells you to do. maybe try about 3/4th pound at first and then drive to get the air flowing through the condenser and note the inside temp after a few minutes. cleaning the condenser and radiator cooling fins is a good idea and check between the cond. and Rad. for leaves and debris. One smart idea also is to check with the last owner to see if he added the correct compressor oil R-134 oil, this is a requirement to keep the compressor alive. most of the time shops add a label under the hood to let you know the correct oil and charge weight.