A/C compressor isn't coming on - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 08-10-2009
dakota772's Avatar
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A/C compressor isn't coming on

There is a very long story behind this, but I'm sure most of you aren;t interested in that so here are the details.

I have a '00 3.0L 2WD, I recently changed out the compressor since the one I had has not worked for the past 2 years. After having the system charged, the compressor will not turn over. We did some quick tests at the shop and found that the compressor works, but it is not receiving a signal to turn on (disengage the clutch). At first we thought a fuse or relay may be blown. The tech checked all the fuses in the engine compartment and under the dash, all are good. I replaced the WOT relay, but that didn't fix it. We bypassed the harness and connected the compressor directly to the battery and it switched on. So, we know the compressor is okay, fuses and relays are okay, any ideas where the problem could be?

I have been looking forward to A/C for so long in this desert sun. I cannot wait to get this problem fixed and stay cool.
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Old 08-10-2009
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check the low pressure(clutch cycling) switch. other than that, get a wiring diagram of your compressor control circuit and start testing.
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Old 08-10-2009
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good luck....mine was a combination of the ECU being fried, wiring problems, and a vacuum leak
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Old 08-10-2009
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Stick a pressure gauge on the low side.

The system will not work with no charge or too much charge.

After that its an electrical issue.
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Old 08-10-2009
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Quote:
Originally Posted by Blhde View Post
Stick a pressure gauge on the low side.

The system will not work with no charge or too much charge.

After that its an electrical issue.
x2, plus, when yall put voltage straight to the compressor, did it cool? my first post was assuming you had a full, proper charge.
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Old 08-11-2009
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Quote:
Originally Posted by Blhde View Post
Stick a pressure gauge on the low side.

The system will not work with no charge or too much charge.

After that its an electrical issue.
They charged the system with ~1.4 lbs of R-134. So, if I put a gauge on the low pressure side, how will I know if it is over charged? Thanks for the help.

I know the ECU and all other electrical components are fine because I'm not having any other problems. Before I did the engine swap, the A/C system worked fine. After finishing the swap, I had the system charged about 2 years ago and they said I had blown a rear seal on the compressor. After saving up for the past 2 years to buy all new parts for the A/C system, I found that the problem was a missing o-ring on the back of the compressor. So, I replaced the old compressor, orifice tube, and accumulator anyway. And this is where I'm at.

Silver - where is the low pressure cycling switch?

Thanks for all the help guys. I will keep you updated as I try your suggestions.
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Old 08-11-2009
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When you hook up a gauge you need to know the operating pressures of the a/c system. I do not know what those are though. This will tell you if the system is operating correctly and if it is low/high on refrigerant. Do you have a A/C manifold gauge?
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Old 08-11-2009
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Quote:
Originally Posted by FullThrottle02 View Post
When you hook up a gauge you need to know the operating pressures of the a/c system. I do not know what those are though. This will tell you if the system is operating correctly and if it is low/high on refrigerant. Do you have a A/C manifold gauge?
I don't a have an A/C manifold gauge. Where can I get one...Sears? How can I find out the operating pressures for the system? Would be in my Haynes manual?
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Old 08-11-2009
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Quote:
Originally Posted by dakota772 View Post
They charged the system with ~1.4 lbs of R-134. So, if I put a gauge on the low pressure side, how will I know if it is over charged? Thanks for the help.

Most pressure gauges you can pick up in the recharge section at the auto parts store will have a green area.

IIRC its like 18-25psi. The gauge instructions should lay it out for you.

The low pressure cycle switch is pretty much next to the low side port. On the firewall near the blower fan. Mounted on the black cylinder.
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Old 08-23-2009
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My compressor is working great as of last night. After lots of troubleshooting and electrical testing, it turns out that the problem was simply an unplugged sensor. The high pressure side was not plugged into the harness.

I know that when I dropped it off at the shop to have the A/C charged, everything was plugged in and ready to go. So, either the shop is too stupid to realize they needed to plug it back in or they were trying to rip me off so that I would have to pay them to "diagnose" the problem. My guess is they were trying to rip me off. It seems like shops don't like it when you do 90% of the work yourself, the A/C charge and the alignment shops have both been painful. Thanks again for the help guys!
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