A/C Fan Clutch

Yesterday my wife calls to say that AC on the burb is not working. When I got home, I found that the compressor was not spinning. I checked the relay by swapping it with the Starter relay, the relay was okay so I swapped them back to their original spots. I then checked all of the electrical connections, all seemed okay, but the compressor still didn't engage. I then tapped on the center of the compressor (the part that wasn't spinning) while the enging was running and it spun. Everything now works fine.

So I suspect the A/C clutch is going out. Where can I get one at a reasonable cost? Are there any special tools needed to change it? Its a 97 suburban with the ac at the top of the engine.
thanks.

Try www.marksair.com for A/C parts.

The description in the service manual indicates some special tools are needed to R&R a clutch.

Jim

Thanks, by brother in law has the service manual set for a 98, I think they are the same. I will check that out.

Is the system charged? My compressor will not kick on if there is not sufficient pressure in the system.

I believe it to be charged, the compressor was replaced at the dealer the summer before last, 1500 bucks for that one. I know that doesn't really say much but it cools great once it kicks in. I was thinking that the clutch was worn. Maybe there's an electrical issue preventing the clutch from engaging?

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Originally Posted by surfbeetle

I believe it to be charged, the compressor was replaced at the dealer the summer before last, 1500 bucks for that one. I know that doesn't really say much but it cools great once it kicks in. I was thinking that the clutch was worn. Maybe there's an electrical issue preventing the clutch from engaging?

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Check your charge.

No charge, no compressor kick in. Is a safety feature so the compressor is not pumping dry.

Matt

Please correct me if I am incorrect, but my understanding was that if the safety were to not allow the compressor clutch to engage because of low freon, then it would not engage at all until refilled.

That is not what is happening, it will engage if you lightly tap the center of the compressor pulley while the engine is running. You then can turn it on and off with no issues. Then at some random point, it won't come back on. Then you can tap the center and will come right back on blowing cold. I plan to check the levels, but I am open to all suggestions.
Thanks again.

Quote:

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Originally Posted by surfbeetle

Please correct me if I am incorrect, but my understanding was that if the safety were to not allow the compressor clutch to engage because of low freon, then it would not engage at all until refilled.

That is not what is happening, it will engage if you lightly tap the center of the compressor pulley while the engine is running. You then can turn it on and off with no issues. Then at some random point, it won't come back on. Then you can tap the center and will come right back on blowing cold. I plan to check the levels, but I am open to all suggestions.
Thanks again.

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If it engages when you "tap" the clutch, then the electromagnet is too weak for one reason or another. Could be low voltage (poor electrical system condition, alternator, and/or batteries), excessive impedance (resistance in the wiring/connections and/or burned/worn switch(es), poor ground), or a damaged clutch winding (internal to the E-mag). Measure the voltage at the compressor connector when it is supposed to be engaged (should be within .2-.5V of batt voltage). If it's too low, apply direct battery voltage to the connector. It should "snap in" sharply. If it seems to work correctly with direct battery voltage, but doesn't when wired normally, you have an issue with the wiring circuit. Most likely a poor ground somewhere (not that grounds are ever a problem on these trucks:D).

It is possible, but rare, the clutch friction material has worn to the point it has too little mass, and/or the gap is too great, to self engage. It is also possible heat cycling and years of service has increased clutch spring tension.

Isn't there a brush and slip ring in there?

DmaxMaverick,
Batteries are new, alternator is new, voltage guage reads 14. I guess I will check the voltage at the compressor as you said. The compressor was replaced by the dealer two years ago, I assume that it came with a new clutch on it, but you never know. Thanks for your insight on the electrical end of things.

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Originally Posted by JohnC

Isn't there a brush and slip ring in there?

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Good question. The old axial pumps do. Later do not. The radials since 80-something shouldn't, and recip's followed the radials. None of them since 1997 should have one, as the EM's are stationary. None of this applies to aftermarket mfg's, your guess is as good as mine. It's best to just look.