Just got back from the AC shop. Their machine recommended 2.25 lbs of R-134a which is 90% of the R-12 capacity. My AC system is working well and the old compressor is running smoothly and quietly. The only thing I'm not sure of is if the switch is adjusted for maximum performance. I had it turned back and the mechanic said it was going to freeze up like that so he turned it clockwise a quarter turn which is HIGHER than where it started from. Anyway, it is blowing cold.
Get a vent thermometer and drive the car around at highway speeds for 20 minutes or so. Anything under 40F is acceptable. Otherwise hook up a gauge set and adjust it back to 21 psi. He might have a more accurate gauge set, or not be aware the adjustment is needed with conversions.
Where I had it set, it was not cycling. He said it would freeze up like that so he adjusted it back clockwise. I'll find a meat thermometer and see what I come up with.
I got a thermometer and the AC is blowing really cold in the 40s*F. It is only working intermittently, though. I decided to eliminate the pressure switch from the list of possibles. I bought and installed Four Seasons Part# 36674 which is the correct part for R-134a retro-fits. It did not solve my problem.
So then I decided to change the relay that is mounted behind the driver in the engine compartment. It is the one that looks just like the fuel pump relay. The AC relay is supposed to be mounted toward the passenger side of the fuel pump relay. Although they look the same on the outside, the AC relay is different because it has a diode built into the circuitry. I'm still searching for that ACDelco part number. So anyway, I swapped a different relay onto the AC harness. It did not make any change good or bad. I'm going to find that part number and buy a new one with the diode just to make sure.
I have noticed that revving my engine can re-start the AC after it has quit. If I stomp on the gas and give it a good jolt from kicking down a gear, the AC will often come back on. After a bit more reading, I have found that I may need a new wiring pigtail that connects to the top of the compressor. It is ACDelco part# PT179 Compressor Clutch Connector. I am going to get one of these and give it a try also.
I got a thermometer and the AC is blowing really cold in the 40s*F. It is only working intermittently, though. I decided to eliminate the pressure switch from the list of possibles. I bought and installed Four Seasons Part# 36674 which is the correct part for R-134a retro-fits. It did not solve my problem.
So then I decided to change the relay that is mounted behind the driver in the engine compartment. It is the one that looks just like the fuel pump relay. The AC relay is supposed to be mounted toward the passenger side of the fuel pump relay. Although they look the same on the outside, the AC relay is different because it has a diode built into the circuitry. I'm still searching for that ACDelco part number. So anyway, I swapped a different relay onto the AC harness. It did not make any change good or bad. I'm going to find that part number and buy a new one with the diode just to make sure.
I have noticed that revving my engine can re-start the AC after it has quit. If I stomp on the gas and give it a good jolt from kicking down a gear, the AC will often come back on. After a bit more reading, I have found that I may need a new wiring pigtail that connects to the top of the compressor. It is ACDelco part# PT179 Compressor Clutch Connector. I am going to get one of these and give it a try also.
The relay doesn't have the diode, the diode is part of the compressor clutch coil connector (the wiring pigtail).
The relay doesn't have the diode, the diode is part of the compressor clutch coil connector (the wiring pigtail).
According to this thread among others, https://www.fiero.nl/forum/A...110502-2-105426.html the fuel relay and AC relay only appear to be the same outwardly. However, the AC relay has an internal diode and the two relays have different part numbers. I doubt my relays are in their correct original position anymore so I can't trust which part number is where. I could check them for different numbers and post them.
I agree the pigtail has a diode also. Available from Rock Auto but not locally.
The relay has a diode, but it and the fuel pump relay are still interchangeable. The one that typically goes bad is the one at the compressor coil connector. You can check both with a meter/continuity tester. Should also have 12V at terminal B when the AC control head is in any AC mode, that will tell you if it's working without wasting $10 on a new one.
I agree they are interchangeable but that is usually recommended as a quick test and fix for a failed fuel pump relay. You don't really hear about swaps in the other direction for obvious reasons. I have to think the AC relay has the diode for a reason so I want the correct part in there. I just don't know which part number is the correct one.
As long as I have to order from Rock Auto for the clutch pigtail anyway, I figured I should get the relay also.
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