Trying to charge my AC

Hello all. New to Pontiac. New to this forum. I have an 86 Fiero GT. I have no experience at all with this but, my AC wasn’t working, and it was the original R12 system. So I purchased a retrofit kit and a gauge set and here’s where I’m at.

Originally there was no pressure at all in the system so I replaced all the O-rings on the accumulator and the orifice tube without worrying about recovering any R12. I then pulled a vacuum on the system for around an hour and then let it sit for a while and verified that the gauges held at -30.

Using my manifold I put 8 oz of ester oil into the system and no leaks and it still held pressure.

Then attempted to charge the system using 12oz cans I bought from parts store. Turned AC on high and hooked can up to manifold but refrigerant never leaves the can and the pressures never rise in the gauges. I’m getting power to the low pressure switch but the switch is not turning on the compressor relay. If I jumper the low pressure switch I can verify the relay gets voltage on the load and control side and I hear the relay click and the compressor clutch kicks in, but even then the system won’t charge through my manifold via the low or the high side.

I get that the low pressure switch won’t kick on the compressor when it’s completely empty like it is, but I don’t get it how it supposed to charge it initially. Is it through just vacuum that it should pull from the refrigerant can? How can I get this system charged? I feel like I’m so close. Can anyone help?



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Let’s see if I have this straight.

You didn’t remove any of the mineral oil for the R12 AC system, but you added 8 oz’s of ester oil to the system for the R134a?


Vac pump is hooked up to hose and than to gauge set. Hoses goes to hi/low side ports. And you know hose connectors are able to flow into ac system? How? Maybe you are only drawing vac on hose itself? You have vacuum in system. Opening can port should dump the entire can into system. With motor off.

I guess I don’t know for sure, but my hoses are connected to the service ports and I can see the gauge move a bit when I force the compressor on, so I just assumed that I was pulling a vacuum on the whole system. I ordered a new can tap
yesterday. Thinking maybe the one that came with the gauge set is crappy. It’s not like a one you normally see for sale. Maybe that explains it?

How do you clear ac code to allow compressor on initially? Disconnect battery? An older fiero should run compressor for a few sec after starting motor.

Ok that’s a good idea. I’ll try that.

I’m not knowledgeable on AC, but I believe that replacing the accumulator drier is always highly recommended when a system has become exposed.

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It’s something that is done at the same time as a recharge. It prolongs the life of the system. Basically, it’s a little can of dessicant on the refrigerant line. It removes water and traps it inside gel beads.

Charging it initially is done by jumping the low pressure cut-off switch. It may take a can before it starts cycling on and off with the switch connector plugged back in.

You should feel the can get cold IF the system is accepting the charge. In some cases systems may be slow to take a charge. In those cases I lower the refrigerant can into a fairly large pan of very hot or boiling water. Careful with that though.

Yes, you are right about the accumulator. It only take a tiny bit of moisture to cause the system to become inoperative when the moisture freezes around the expansion valve or orifice tube as the case may be.