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Discussion Starter · #1 · (Edited)
Did some troubleshooting for the compressor not engaging, bypassed the low pressure switch and I am getting about 12V there, but measuring at the cable that goes to the compressor, there's no voltage there (engine not running, AC green light on, blower at mid power, and low pressure switch bypassed)

It seems there's no ac fuse, and could not find the ac relay, if there is one.

Any ideas?
 

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The wire going to the ac clutch will only have 12v when the engine is running and the car is allowing the ac to run. (proper pressure, proper temps)
 

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When was the last time Freon was added to the system? If your a lb low, the system may not come on.
 

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It should be acting normal then. Add two complete 12oz cans of R-134A refrigerant (Freon is actually a dated term for R12, not used anymore!) and the system should theoretically work. Once the proper amount of refrigerant is in, you can further diagnose problems if they exist.

Without refrigerant in the system the compressor should never engage, and diagnosing A/C system issues are much harder.
 

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It should be acting normal then. Add two complete 12oz cans of R-134A refrigerant (Freon is actually a dated term for R12, not used anymore!) and the system should theoretically work. Once the proper amount of refrigerant is in, you can further diagnose problems if they exist.

Without refrigerant in the system the compressor should never engage, and diagnosing A/C system issues are much harder.
Can't help the terms, hell I'm 60, but your advice is spot on. If the compressor is new, it is also customary to replenish with a can of charge oil, at least that's the way we did it in the R12 days. The system needs oil in the refrigerant charge to lubricate the compressor.
 

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Forgot about the oil part, good catch! The whole system capacity is 6.8oz, assuming every component is dry. I believe just changing the compressor warrants about 3-4oz of oil if I remember right.
 

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I would hope that if you had the system open for a compressor replacement you also replaced the accumulator and the orifice tube. Also, you really need to pull a vacuum before you recharge it if the system was open.
 

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Autozone lists the vacuum pump as a free rent-a-tool, I found this out last time I did the job. Pretty decent pump, and it's always in good shape because hardly anyone ever vacs their own A/C system. You'd just need to get some manifold gauges from harbor freight (or equivalent) to connect it to your system.
 

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I would hope that if you had the system open for a compressor replacement you also replaced the accumulator and the orifice tube. Also, you really need to pull a vacuum before you recharge it if the system was open.
Banana hasn't responded to any of this. Didn't now how much of this process 'WE' should assume that he knows. Pulling the system to a vacuum was an absolute must with R12, because R12 and H2O combine to make hydrochloric acid. Obviously R134 would make something else equally as undesirable. At sea level, and 29 inches of vacuum, H2O boils at about 50 degrees F, so the vapors are evacuated. You should pull a vacuum for at least one hour. Close your manifold gauges, and wait another ten minutes or so in this condition to make sure that the system can hold a vacuum. If not, you have a leak somewhere you need to attend to. If it holds a vacuum, that condition greatly aids in pulling in the first can of refrigerant. I like to start with the charge oil, and use the rest of the charge to circulate it from the start.
 

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Discussion Starter · #11 ·
Thanks for your answers.

Have done all the things stated above.

My question is very specific, no voltage at the compressor cable, the other things are more related to maintenance of the AC system.

Have tried again but this time with the engine running but still nothing.

Swapped the AC relay from my other car, and still nothing.

Any other ideas?
 

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You need to jump the low side pressure switch electrical connector (at the firewall) with a paperclip in order to get the compressor to suck the first can, in most cases. The system won't have enough pressure to operate and get the 12v to that wire unless there is the correct amount of refrigerant in the system. Make sure you don't bypass this switch unless you have a full can of refrigerant hooked up. Once the first can is in, remove the paperclip and it should take the next can on it's own.

That wire engages the clutch which engages the compressor. It will never engage without refrigerant, since the system doesn't want to destroy itself.
 
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