QuestionQUESTION: A/C compressor clutch does not engage.
Fuses all checked okay.
Unhooked the low pressure switch and jumped it with a paper clip. With the engine running,a/c on max it still would not engage.
Low side read zero.
Added a 13 oz. can of freon.
Low side now reads 12 lbs. Clutch still not engaging.
Disconnected the clutch electrical connector cleaned
terminals, reconnected, restarted engine and the compressor still not engaging.
Any help would be greatly appreciated.
ANSWER: Charlie,
Thanks for the question, I hope I will be able to help. Please don't think that I am trying to insult your intelligence at any point in this, I just want to make certain we are on the same page.
The switch that you bypassed, are you certain it was the low pressure switch, and not the high pressure switch. The low pressure switch is usually located on an aluminum canister about the girth of a soda can with two lines coming out of the top. Your system may have a receiver in the system that looks similar, except for the fact that the receiver lines usually have lines with fittings on them connected to it, rather than the accumulator's hard lines. The high pressure switch will usually be located on the receiver, so they can be confused for each other.
Ok, with that out of the way. With the low pressure switch jumped, what is your voltage reading at the compressor clutch connector? There should be 12 volts. If you read voltage, check your compressor ground wire, it could be a loose connection, or have corrosion built up on it not allowing it to find ground, and just needs to be cleaned. If you do not have a voltmeter. You can run an insulated wire from the + side of your battery to the clutch input wire and it should snap together. If it does not snap, check your ground, if it doesn't.......
With the low pressure switch jumped, a good ground, and the fuse good, typically my next check is the AC clutch relay. Locate your relay and check it. On most 12 volt relays, there is a drawing of the contacts on the side of it. You will have 2 contacts which are your control voltage to the coil, and 3 contacts for your power to go to your clutch. I will call the coil points A and B. The contact bringing power from your control unit into the relay contacts C, A dead end contact for when the relay is open (not sending power to your clutch) D, and the wire out to your clutch E.
First check terminals A to B for continuity. You should read resistance, or hear a beep, depending on what type of multimeter you are using. Then Check terminal C to D. Again you should have continuity. Then check terminals C to E and you should not have continuity, it should be open. If all of that checks out so far, check the input wire to terminal A. You should read 12 volts with the A/C on and the switch in the run position. If you do not read any voltage here, then the problem is further back in your system towards the control unit. Without the schematics here in front of me, I can't tell you where to check next. If you do have 12 volts at the coil wire....
Apply 12 volts to the coil contact, When you do you should read 12 volts on both sides of the coil. (A to ground and B to ground) So far so good? You should now be able to read 12 volts at E. If you do not, then the relay is bad and needs replacing.
An easier way to check the relay if I was confusing in my instructions above (I lose myself sometimes)... with your AC on and Ignition in run position, disconnect the relay and plug it back in, you should hear a soft click. That is your contacts changing position. If you do not hear it check Terminal A for 12 volts. If you have voltage there, replace the relay, If you do not have voltage there, the problem is between your relay and control panel. Either in the wiring, or in the control panel itself.
I believe you will find your relay to be bad. If it tests good, depending on your skills with schematics and wiring, you can troubleshoot it further, or take it to a service shop and see what they find.
I hope I was of a little help.
---------- FOLLOW-UP ----------
QUESTION: David,
Your help is greatly appreciated.
I don't have a volt meter, so I jumped the low pressure switch again and using a test light at the two wire connector (green and black wires) the green wire had power the black had none. My guess is the black is a ground. I stripped the black wire back and ran a wire from the black wire to a good engine ground and still did not get the clutch to engage. Could it be a bad clutch coil?
I would have checked the relay but couldn't find it.
AnswerCharlie,
If you had power at the clutch hot wire, and gave the compressor a good ground, It should have engaged. The opnly thing there is between those points is the compressor clutch, so I would safely say the clutch has gone bad. But I dont like giving less than 100% information. So just one more check to confirm it is the clutch.
Run a good ground to your black wire on the compressor. Run a wire from the positive side of your battery, and touch it to the green wire on the compressor. If it does not snap, Then it is without a doubt the clutch.
Some shops have the capabilities and tools to replace just the clutch, but 9 times out of 10 it is close to the same cost to replace the whole compressor. But ask around. Alot of factors play into the cost and with an A/C shop doing it, you are looking at between 300-500 bucks.
Hope I helped.
