02 a/c clutch testing
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02 a/c clutch testing
Hey guys,
I have an 02 EB with the 4.6. About a week ago, the a/c quit working. I first suspected low freon, but my gauges tell me differently. I bypassed the pressure switch and still the clutch does NOT engage. I unplugged the connector to the clutch. When the a/c is active, I have 12-14v at the connector. I checked and I have that voltage by either grounding to the chassis or to the other pin on the connector. So I believe my clutch is bad, but as a last test, I want to make sure. How can I test the clutch? Also, is there any way to replace the clutch without removing the compressor from the vehicle????
Bryan
I have an 02 EB with the 4.6. About a week ago, the a/c quit working. I first suspected low freon, but my gauges tell me differently. I bypassed the pressure switch and still the clutch does NOT engage. I unplugged the connector to the clutch. When the a/c is active, I have 12-14v at the connector. I checked and I have that voltage by either grounding to the chassis or to the other pin on the connector. So I believe my clutch is bad, but as a last test, I want to make sure. How can I test the clutch? Also, is there any way to replace the clutch without removing the compressor from the vehicle????
Bryan
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Joined: Jun 2009
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From: Cedar Rapids, IA
Did you check for voltage to the connector using a DMM or a test light? A DMM has such high input impedance that it won't help you confirm that you have enough current drive to a circuit. The test light puts more of a load on the circuit and for these higher current draw applications may give you a better indication. If you don't have a test light and don't want to purchase one, then you could try plugging the field coil back in and backprobing the connector using the DMM. Do you still have the same voltage reading? If so, the coil probably has an open circuit. The ground for the circuit is completed by the coil through the connector. If the voltage drops to just several volts it may be trying to pull the clutch in but the spacing is too large. If it drops to a volt or two, then you either have too little supply current (corrosion in the circuit, leaky reverse biased diode, etc.) or a nearly shorted field coil. I would expect a completely shorted field coil or diode to blow a fuse somewhere.
-Rod
-Rod
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Joined: Feb 2006
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From: Lorain County, Ohio
Here's a quick test:
With the engine running and the AC turned on, CAREFULLY tap the front of the compressor clutch with a stick, screwdriver handle or other suitable device.
If the clutch engages, the clutch gap is too wide. You can adjust the gap by removing the clutch plate and discarding the shim inside.
With the engine running and the AC turned on, CAREFULLY tap the front of the compressor clutch with a stick, screwdriver handle or other suitable device.
If the clutch engages, the clutch gap is too wide. You can adjust the gap by removing the clutch plate and discarding the shim inside.
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I used a dmm to check the voltage, not the current draw. I checked all the fuses and relays; all are good. At this point the clutch doesn't engage. I'll try the tapping method and also see if I can figure out if there is any kind of current draw. So assuming the clutch is bad, do I have to remove the compressor to pull the clutch or is there a method to change it without venting the system and removing the compressor?
Bryan
Bryan
Fleet Mechanic
Joined: Feb 2006
Posts: 1,776
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From: Lorain County, Ohio
A DMM isn't the best thing for testing as it doesn't put a load on the circuit. If there is high resistance in the circuit (burned relay contacts, etc), the meter "can" still read +12v. A test light will add some load to the circuit
With that said, it sounds like the gap is too wide or the clutch coil is open. The clutch coils rarely fail so my money is on the clutch gap. If it's greater than about .025"-.030" it is too wide and can't pull in.
If you have room to remove the center bolt, the clutch plate will slide right off. You may have to coax it to move with a couple of screwdrivers on opposite sides of the clutch. Usually, all that is needed is to remove a single shim (or the only shim) down in the splined hole that slides over the compressor shaft.
Be sure to use a dab of Loctite on the bolt and don't overtighten it. If you break the bolt you will have to pull the compressor.
Edit: I didn't see shorods reply before posting. Sorry.
With that said, it sounds like the gap is too wide or the clutch coil is open. The clutch coils rarely fail so my money is on the clutch gap. If it's greater than about .025"-.030" it is too wide and can't pull in.
If you have room to remove the center bolt, the clutch plate will slide right off. You may have to coax it to move with a couple of screwdrivers on opposite sides of the clutch. Usually, all that is needed is to remove a single shim (or the only shim) down in the splined hole that slides over the compressor shaft.
Be sure to use a dab of Loctite on the bolt and don't overtighten it. If you break the bolt you will have to pull the compressor.
Edit: I didn't see shorods reply before posting. Sorry.
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Just to follow up on this thread, I checked the resistance across the two terminals on the coil and it came up to about 100,000 Ohms. So, the coil is bad. I already picked up a replacement at NAPA and will try to tear down this week. When I find out exactly what happened (if I can), I'll post it here.
Bryan
Bryan
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