How to test the AC compressor?

[neemo6]

My ac has suddenly stopped working. When trying to recharge it with the r134, will not take anymore as it already fully charged. Testing the electrical signal to the compressor gives me sporadic readings, although other than 12-14v steady like other cars im not too sure as to what this should read. Any ideas, tips, or help as to what I should be checking for on my ac compressor?

[jacobsen]

What do you mean it will not take any more because it's full? The system will take about five hundred grams of R134a.

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[neemo6]

Yes,the system is full as there are no leaks.

[jacobsen]

Is your compressor working? Or when you try to turn on the AC does the economy light turn on? If you overcharge the system the AC will not work and if there is not enough charge the AC will not work. Typical behavior of too much refrigerant or too little refrigerant is for the economy like to come on when you try to turn on the AC. What is your low side PSI with the vehicle running? What is the low side and high side PSI with the motor cold? If you have no leaks, the correct amount of charge and your valves behind your glove box are working correctly, it could be your fan sensor. As OG recently mentioned. Do your AC fans come on?

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[neemo6]

Im dont know if the compressor is working. That is why I was wondering as to how to test it. I do not have an economy light that comes on. I do not recall what the pressures were but they were not out of the norm. The valves behind the glove box all seemed to be actuating properly. The fans were not coming on. Last year during summer the ac system would just stop working after about 10-15 minutes if the car sat idling, but would come right back on blowing cold air again if I simply turned the ignition off and immediately turned it back on. The last time I tried to 'restart' it, the cold air never came back on just kept blowing the non- AC air.

[KHARDa4]

Hook gauges to it. Turn system on. If the gauges are showing equalized pressure on high and low side the unit is not compressing. This does not mean that the compressor is bad it could have to much or to little freon and is turned off due to low or high pressure. I would suggest having a shop completely evacuate the system and recharge as a good starting point. You may have a leak but during the recharge the system is put into a vacuum and would show leaks if they are present.

[neemo6]

Just for shits and giggle i tried to add some freon today, the pressure accorcing to the gauge was 100+ psi on the low side. The fans do not come on. I tried to relive pressure from the low side and it would go down but thenwould slowly rise again, not sure what its doing here. Any ideas?

[jacobsen]

Your first statement about your system not taking any more R134a because it's full concerns me. That's not how the system is filled, I'm not saying that that's what you did. It's just that that's the way it sounds. It's not a fuel tank and which you filled to the brim. simply put in 500 grams plus or minus 20 grams. The trouble is any time you're working on the air conditioning system and the compressor is not working there's no way to tell how much gas is really in the system unless you completely evacuated and start over. it's possible you overfilled the system and the compressor safety switch is preventing the compressor from turning on. It's possible there is not enough in the system and the compressor is not coming on. It's possible for you to have a clogged or broken restrictor valve which is causing the pressure to equalize and preventing the compressor from coming on. It's possible your fan switch is not working. You should check for any HVAC fault codes at this point.

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[KHARDa4]

What are the high and low pressures with the system on and running? It's hard to diag if you're using a refrigerant can from AutoZone.

[jacobsen]

What are the high and low pressures with the system on and running? It's hard to diag if you're using a refrigerant can from AutoZone.

He can't get the compressor to come on so we don't have any way to know that. He's not getting voltage to the compressor. But apparently it's a variable input so I'm not sure how that part of it works completely. He needs OG or diagnosticator for anything technical.

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[GR42AI]

I'm having a similar issue, drove the car all day yesterday and the A/C worked great. I did let the car idle for about 30 minutes in 100deg heat because I was having battery issues, the A/C stopped working till the temp went back to normal. Today using my ross-tech cable I noticed that the ACHigh was on but compressor was off and it blows warm now.

[jacobsen]

I'm having a similar issue, drove the car all day yesterday and the A/C worked great. I did let the car idle for about 30 minutes in 100deg heat because I was having battery issues, the A/C stopped working till the temp went back to normal. Today using my ross-tech cable I noticed that the ACHigh was on but compressor was off and it blows warm now.

Time to check your high and low side pressures. Sounds like you have a leak. But again the trouble stems from the AC compressor not coming on at all. You can try to give it a little bit of 134 and see if it comes on again. Now the question is, is your economy light coming on when you try to turn the AC on?

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[neemo6]

No the light doesnt come on automatically, it will come on if i press the button. The compressor was replaced last year with a used one that i bought locally. The r134 was filled at the time and it worked great other than when the car would idle for a bit and the ac would all of a sudden just stop working with the immobilizer light flashing, until i turned the car off and then on again, and wuld work great again. Up until early this summer that it would not work even after a restart. Fans are not coming on, there is power at the plug to the compressor, pressure according to autozone gauge was a t 100+psi, pressure rises when releasing pressure from low side, flaps under glove box move accoedingly, im at a complete loss here, really do not want to buy a compressor and still have the same issue.