951 AC question

[White951]

I started messing with my air conditioner on my 1986 951. Bought the car 2 years ago w/ 28k miles on it, ac not working. I hooked up a gauge the other day and it read zero psi on both high & low sides with the car not running. no pressure when running. I put in on 13 oz can of r12. Pressure is now 80psi on both sides stopped and running. compressor won't engage. outside temp was 85. next morning gauges said 30psi both sides outside temp 78. I am not sure if it leaked out or it escaped when I hooked up the gauges. I will test for leaks. But the fact that the compressor would not engage with the pressure at what it was is my issue. Should the pressure have been so high with only 12 oz of a 33.5 oz system? Do I possibly have an electrical problem with the clutch or low pressure switch. I think the first thing I will do is test for leaks. Also I did not bother to try to pull a vacum first. Is this bad?


John

[mike944]

I'm not sure why your compressor isn't coming on. But i'll try to answer your other questions. Yes, it's entirely possible that it all leaked out overnight.

When was the last time the AC worked? if it hasn't worked in two years, and the car only has 28K on it, it probably hasn't worked in 5 years or more. It's leaking because the seals are completely dried out. When an AC doesn't get run regularly, the seals dry out, and the system starts leaking. After the system leaks out, the seals get drier, and drier, and drier. You don't have much choice but to replace them all. You should be able to find a pre-packaged kit for this. You could try to put some leak sealer in the system instead, but you probably have a leak at every connection in the system, and you'll be filling it with refrigerant constantly, which will be alot more expensive than the seal kit.

Because the system has been unfilled for 2 years, you will need to replace the reciever/dryer too. It's probably contaminated. You would probably be better off in the long run if you buy seals, and a reciever/dryer for R134a. Doing the conversion this way is the "right way" to convert to R134a, and you should never have a problem with your system again.

While your system is apart, you can also check / replace the pressure switch.

A few words about your charging technique: YES you need to vacuum out the system. you need a good vacuum pump to do this. If it's been empty for years, i'd leave the vacuum pump connected for a few hours. Also, you did not state that you added oil to the system. All AC systems need compressor oil. The oil quantity should be listed next to the refrigerant quantity. Make sure you put in the correct oil for the referierant you use. It's available in presurized cans, just like the referigerant. It's this oil that keeps the seals from drying out.

Mike