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  #1  
Old 08-28-2006, 04:36 PM
deltajetfixer's Avatar
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W210 Compressor clutch slipping?

I don't have much experience with repairing air conditioning but here's the story:

Today I noticed the lack of cold air from the vents when the AC was "on". Plenty of airflow, just no cooling.

Auxiliary fans are not coming on nor is the compressor engaging.

Found the info on obtaining the Actual Values and came up with reasonable numbers (range from 95-111 degrees F)for all the temperature sensors. The refrigerant pressure reads "08" which seems legitimate with no compressor operation.

Codes pulled are:
B1419 Electromagnetic clutch
B1226 In-car temperature sensor
B1234 Sun sensor

Here's the wierd thing. The compressor clutch is producing a burned smell with the climate control set to OFF. You can hear it and see it barely making its way around in rotation about an 1/8th of an inch at a time per revolution. It sounds like a dragging brake disk. I can also move the clutch by hand quite easily.

I just replaced the coolant, fan clutch, aux fan belt, and main belt and the car was operating fine until this afternoon.

Oh yeah, if anyone can tell me where the fuse is for the clutch, I'd really like to know about it. I've been through all three fuse boxes and can only find one labled Blower Motor AC.

Ideas? Thanks in advance!
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1998 M3
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Old 08-28-2006, 05:40 PM
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Disconnect the wires going to the compressor to disengage the clutch. Try to turn the inner part of the pulley (on the front of the clutch) and see if the compressor is seized. Is the "EC" light on on the AC control panel?
Gilly
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Old 08-28-2006, 05:47 PM
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A dragging clutch would heat up the pully. That could blow the thermal fuse which is built into the clutch.

See if you have continuity across the clutch windings.
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Old 08-28-2006, 06:06 PM
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Quote:
Originally Posted by Matt L View Post
A dragging clutch would heat up the pully. That could blow the thermal fuse which is built into the clutch.

See if you have continuity across the clutch windings.
I'd LOVE to test the continuity but it'll have to wait until the morning.It would REALLY be easy if there was an associated fuse for the sucker but I can't find it!!! Probably controlled by some computer somwhere.

I'm aware of the thermal fuse. From what I've read in my copy of WIS, it seems to indicate that a seized compressor would generate enough friction to set it off.

This thing is slipping ever SO slightly. I fear with the new engine fan clutch I installed a week ago that the underhood temps have been reduced to the point where this tiny amount of slippage won't melt the thermal fuse! I can rotate the clutch easily by hand so I doubt the compressor's seized.

I'm just curious as to why a compressor clutch would fail in this manner? Maybe a return spring is broken?

Would you happen to know if it's possible to replace just the clutch on this beast without possibly removing the refrigerant lines? Clutch is about $150 versus $600 for the compressor. Only thing holding me back in figuring out how I would hold the compressor shaft still to remove/install the clutch. WIS doesn't detail the procedure.
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Old 08-28-2006, 09:22 PM
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OK, there is the outside of the pulley, the part the belt spins, and the inside of the clutch, the part that rotates the compressor when the clutch is engaged. You just need to hold the inside part of the clutch and I believe you'll see a nut in the center which is removed to take off the clutch and pulley assembly, so no need to take off lines and can be done on the car. Not sure what's used to keep the inside of the clutch from rotating, I believe that nut is pretty low-torque, may be able to hold it by hand.
Gilly
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Old 08-29-2006, 09:52 AM
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Quote:
Originally Posted by Gilly View Post
OK, there is the outside of the pulley, the part the belt spins, and the inside of the clutch, the part that rotates the compressor when the clutch is engaged. You just need to hold the inside part of the clutch and I believe you'll see a nut in the center which is removed to take off the clutch and pulley assembly, so no need to take off lines and can be done on the car. Not sure what's used to keep the inside of the clutch from rotating, I believe that nut is pretty low-torque, may be able to hold it by hand.
Gilly
Agreed. Diameter of bolt appears to be less than 13mm.

Have you ever heard of a clutch failing in this manner?
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Old 08-29-2006, 09:50 AM
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Quote:
Originally Posted by Matt L View Post
A dragging clutch would heat up the pully. That could blow the thermal fuse which is built into the clutch.

See if you have continuity across the clutch windings.
OK. I got to the electrical connection at the clutch windings. They are OPEN. Control voltage to the windings with the panel showing OFF is @6.5-7.0 volts. With panel ON, voltage goes to 13.5.

So here's my proposed plan of attack and please critique anything you find unnecessary. I plan on:

1) Buying a new clutch and installing it. I figure I can keep the shaft from rotating via a strap wrench. The bolt in the center of the clutch looks to be @10-12mm so I figure it's not on that tight.

2) Since the radiator has to come out for optimum visibilty and working ease I'm also considering replacing the waterpump and thermostat/thermostat housing as preventive maintenance. Car has 91500 miles.

Comments PLEASE!
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Last edited by deltajetfixer; 08-29-2006 at 10:16 AM.
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  #8  
Old 08-28-2006, 05:59 PM
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Quote:
Originally Posted by Gilly View Post
Disconnect the wires going to the compressor to disengage the clutch. Try to turn the inner part of the pulley (on the front of the clutch) and see if the compressor is seized. Is the "EC" light on on the AC control panel?
Gilly
I've got the car off so I'm assuming that there's no current going to the clutch.

Clutch turns freely. "EC" light is not stuck on. It illuminates when pressed and goes out when pressed again.
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