A/C Fun, Part 1

My ’97 Chevrolet Monte Carlo’s A/C is dead, and I am going to fix it.

Last fall, towards the end of A/C season, the compressor got really noisy. I could really hear it at low speeds.

Come spring, the compressor won’t engage at all. This probably means a refrigerant leak, faulty compressor, or electrical problem.

You might say that a loud compressor automatically means it’s new compressor time. Not necessarily, says an A/C tech who specializes in GM vehicles: variable displacement V5 compressors can be noisy with too little refrigerant.

My first test is to check the refrigerant pressures. First step is to assemble the gauges:

I tried to hook up the gauges, but I could only manage to get the high pressure side on. Here’s its reading:
That’s not good at all. It’s indicating about 8 PSI, meaning I definitely have a refrigerant leak. I don’t recall exact normal idle pressures, but I am pretty sure it’s over 70 PSI.

I removed the air cleaner box to get good access to the low side fitting. This is looking straight down:

Since I already knew I have a leak, I sprayed in some dye. This dye will help me find the leak later: the dye will appear near the leak point. If it doesn’t obviously show up in daylight, I will be able to detect the leak using a fluorescent “black light.” Here’s the dye can:

You can see how bright the stuff is on the low side fitting:

I got both sides of the gauges hooked up:

I introduced enough R-134a to get the gauges to read about 63 PSI:

I turned the car on and still got no compressor action.

Dang, that’s not good.

At this point, it appears to be an electrical failure. I’ve already gone through all the relays and fuses I am aware of: the fuses in the dash fusebox, and the relays on the front passenger side of the engine compartment. I swapped the relays and fuses out with identical neighboring ones and got nowhere.

I am going to consult with some people before I go on to the next step. However, it looks like I may be in for some “real fun” soon.

3 thoughts on “A/C Fun, Part 1”

  1. I also am having an issue with my 1997 Monte Carlo’s A/C. Last year we tried to get it to take some more coolant with a leak dye in it, but the system didn’t take the coolant b/c the compressor won’t kick on. I didn’t think that the system would take the coolant without the compressor kicking on. My mechanic said that there is a presure switch that I would be able to open with a bobby pin to allow the system to suck up the coolant and that the switch might be keeping the compressor from running. How were you able to get the coolant in the system without the compressor running?

  2. Your mechanic is wrong. This is a 3 wire sensor on the high pressure line, and it does not work like the simple 2-wire switches that used to be on low pressure lines.

    You should be able to pressurize the system enough to turn on simply by connecting a full can of R-134a to it. I was able to get enough pressure to do exactly this from a full vacuum. If that doesn’t work, it sounds like something else may be going on. Have you tested to see whether all the fuses and relays leading to the compressor are working right?

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