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A/C and Clutch

I recently purchased a 1995, 1500 Chevy P/U with a puzzling A/C compressor clutch problem. The engine connecter to the clutch reads 13V and has a good ground but when the A/C system is turned on, the clutch does nothing. However, if the coil is fed directly from the battery, the clutch engages, but there is a very noticable clattering noise. The compressor is working, but correctly, I don’t know. I swapped the A/C relay, check the fuses, and the pressure and switches, all looks good. Any suggestion as to the cause of this problem would be greatly appriciated.

Stephan from New Orleans

Well, there’s low pressure switch in the AC system that prevents the compressor from being damaged if the refrigerant pressure drops too low. When you jump directly to the compressor clutch, you overide this system, and the compressor operates with no refrigerant/lubrication and starts making noise, damaging it.


Sounds like a bad clutch and a bad ground/solenoid together. The clatter maybe one of the clutch pads. The solenoid which puts the clutch in to contact to start the ac either has a marginal coil or you have a bad engine ground. But the good news is that fixing one will fix the other. You just need to replace the ac clutch. Could be money. I do not know how bad it is on the chevy truck but on my ford taurus it was a tough job.

Almost but not quite tester. The person says pressure is good. When an ac clutch pad breaks off it can spin in the ac clutch for a while making a god aweful noise, like bbs in a tin can.

It’s unclear to me if the system pressure is good or not. The OP states “pressure and switches”. Does this mean the pressure AND the switches are good or does it mean the pressure switches are good?

Maybe there’s a poor connection in the clutch wiring somewhere and that 13 volts is basically what I would call a shallow 13; meaning the connection is so poor that it won’t carry enough current to operate the clutch.
A chattering clutch is not good though and maybe there are 2 problems here.

Does the 13 volts remain the same when you have the connector attached to the clutch coil i.e. does the connector to the clutch read 13 volt while it is connected to the coil? I am wondering if there is a high resistance connection somewhere from the Battery down to the clutch connection.

Also check the clutch plate gap. If that is too large the driven plate will not pull in consistently. To adjust the gap you will have to get the remover/installer special tool and follow the prescribed procedure.

Hope this helps.