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Discussion Starter · #1 ·
I know there are a million A/C threads, but mine isn't working and I haven't the slightest clue how to check the system and etc. So here it goes:

I have checked the fuses and swapped the relay - no effect.
Car has been running for quite some time with no A/C now (I would guess a little under a year, but I'm not positive. The big thing that I am stuck on right now is the compressor. I guess I don't understand how to know if it is working... Are there physical parts on the outside that I should see constantly moving? Or should I just hear it turning inside??? My next thought, is to bypass the system to see if I can get the compressor to run by ignoring the high and low pressures. Is that a safe test to try and how do I do it??? If not, what is my next step? How do I test the pressure(s) and what tools do I use?

Thanks in advance,

Air Conditioning Noob - Shane
 

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I know there are a million A/C threads, but mine isn't working and I haven't the slightest clue how to check the system and etc. So here it goes:

I have checked the fuses and swapped the relay - no effect.
Car has been running for quite some time with no A/C now (I would guess a little under a year, but I'm not positive. The big thing that I am stuck on right now is the compressor. I guess I don't understand how to know if it is working... Are there physical parts on the outside that I should see constantly moving? Or should I just hear it turning inside??? My next thought, is to bypass the system to see if I can get the compressor to run by ignoring the high and low pressures. Is that a safe test to try and how do I do it??? If not, what is my next step? How do I test the pressure(s) and what tools do I use?

Thanks in advance,

Air Conditioning Noob - Shane
Best way to test a system is with an A/C manifold gauge set. The set will have connectors that pop onto the high and low pressure ports (different sizes so they only go on one way).

To bypass the controls, I'd suggest you jump the radiator fan relay first to keep the high pressures (if they occur) from getting excessive and causing all your refrigerant to blow out the high pressure relief valve.

Once you've got the fan running, apply 12v power directly to the single wire that goes to the front of the a/c compressor.

If the big pipe at the compressor does not get cold and the smaller pipe hot, than you're out or low on refrigerant.

Do not run the system for very long, just as a quick test.
 

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Discussion Starter · #3 · (Edited)
I'm going to try what you suggested next, but just before I jumped pins 87 and 30 on the A/C Relay and I could see the compressor engaging. I have swapped relay's and the relay works fine else where so that is not the problem. Does this mean that the relay is stopping the system for some reason? and if so, what are the possible reasons?

^^^ is this essentially the same test that you suggested except not as safe?

EDIT: When the compressor was spinning the air did not get cold... Am I out of refrigerant? If so what is the best way to make sure I don't have a leak?
 

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Discussion Starter · #4 ·
UPDATE: I jumped the fan and the compressor so they were both running and the pipes did not change temperature... Should I test for a leak or just assume I am out of refrigerant and try and fill it? If I am out does that guarantee I have/had a leak or does it just run out after years of use?
 

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Nope, use should not matter. I believe the acceptable leakage rate is something like 1 lb per 32 years on an open drive system like a car uses. It's twice as long for a sealed hermetic system like a residential a/c system

If the pipes did not change temp, then yea, you're probably out of refrigerant and you'll need to find and repair the leak.

The kicker is, unless the leak is clearly visible as a mechanical defect in the system, you'll probably need to pressurize the system just to test for the leak.

My personal favorite is to pressurize with nitrogen, combustibles (propane/butane) or oxidizers (o2 or compressed air) are generally a bad idea. In your case, a small can of a/c charge might be the best bet.

To actually look for the leak, a soap solution works well, spray on anything/everything that's part of the a/c system (you'll have to follow the hoses around the engine bay) and look for bubbles.

There are some affordable refrigerant leak detectors, both electronic and propane fueled (old school stuff, works better with R12 found in older cars and R22 in residential a/c systems).

If I use nitrogen, I'll pressurize it up to about 20 psi to use the soap bubbles, or up to about 350 psi and the leaks become clearly audible.

One thing on the electronic leak detectors, most (all?) will give false positive alarms on moving air so if you pressurize the system, turn on the vent fan and stick a leak detector in an air vent, you'll get an alarm nearly all the time.

I won't say evaporators never leak, but they're the least common (but most difficult and expensive to repair) failures. The false positive alert is commonly used by auto a/c repair shops to falsely justify very expensive (and profitable) repairs.

Slow leaks are usually in the soft bits, hoses, valves, o-rings. Rapid leaks are usually in the hard bits, fittings, pipes, condenser or evaporator.

Before you finish up the system and re-charge it, you'll need to replace the receiver/drier (very last thing prior to using a vacuum pump), use a vacuum pump to evacuate the system and then charge the system to spec (usually on a sticker in the engine bay)
 
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