Magnetic Clutch Assembly for A/C

[Rookie2]

I don't think I've seen it discussed here before, but have any of you had to replace the Magnetic Clutch Assembly on the front of the A/C compressor before? Mine appears to have a noisy hiss periodically, after I turn the A/C off.

Thanks,
Rookie2

 

[Rookie2]

Nobody??

Here's a little more background. The metallic hiss occurs after I've turned the AC on for a couple of minutes, then turn it off. It's only hissing when the AC is off. Did the wood dowel trick. Put on the surface of the compressor, and couldn't hear it... put it on the idler pulley bracket, and couldn't hear it... then put it on the pressure plate, on the end of the compressor, and bingo. The FSM refers to this area as the "magnetic clutch" (pressure plate + rotor + stator). So have any of you ever replaced or horsed with this deal??

BTW, the wooden dowel thing is pretty cool, I just had to try it. But I think I'm going to get a stethescope, cause that's an injury waiting to happen.

Thanks,
Rookie2

 

[RavenTai]

I have had vehicles where just after shutting down the AC a muffled hissing noise can be heard in the cab, I figured this was the remaining liquid Freon passing the orifice into the low pressure side in the evaporator, the same thing could happen at the compressor when it is not turning, Freon moving from the high pressure side to the low, never have heard this in the 80.

inside the magnetic clutch there is a bearing, an electromagnetic coil and a clutch, only part that could make noise with the AC off is the bearing, if the bearing were bad it should make constant noise, not only after shutdown,

Does the FSM have any test/checkout info for the clutch and compressor?

I have a mechanics stethoscope, If I remember and have time I’ll check mine.

 

[Rookie2]

Does the FSM have any test/checkout info for the clutch and compressor?

Yes, under the Compressor On-Vehicle Inspection - Magnetic Clutch section, it has a visual inspection for grease at the clutch bearing, and it says inspect Magnetic Clutch Bearing for noise... start engine, check for abnormal noise from near the compressor when A/C switch is off. If abnormal noise is emitted, replace magnetic clutch .

A little odd to me.. if I go out and start it up right now.. no noise. Turn the AC on then off... noise.

In the 3-D blowup sketch, it list three things as part of the magnetic clutch... pressure plate, rotor, and stator. It doesn't specifically list bearing. Do you know if the bearing is inside either the rotor or pressure plate?

I'll inspect closer for grease. I'm also going to double check the belt tension to be for sure.

Thanks,
Rookie2

 

[JDay]

I just replaced all my components a few weeks ago including the clutch assembly. Check the tensioner pulley first. The bearing may be bad and causing the noise.

My clutch made noise all the time, like a scraping metal sound. It turns out someone must have overtightened the belt at some time and cracked the part of the compressor shaft where one of the snaprings is seated. When I removed the clutch assembly I discovered the problem. I ended up replacing the clutch, the compressor, and the filter/drier.

It is easiest to unbolt the compressor from the bracket (leaving the hoses attached) to get the bolt for the pulley and the snap rings off. If you do not have a good set of snapring pliers, buy some.

 

[RavenTai]

looking at the diagrams I would thing the bearing would have to be in the rotor, but I don’t know for sure, I have worked a few compressors not any with a clutch arrangement like that, there are more bearings in the compressor itself but those should not be turning with AC off,

This hissing, is it like hissing gas and is it only short lived after AC shutdown? ( minute or so ) or does it sound more like a noise a bearing would make and goes on for a wile?

Do you have any other problems or just this noise? With the belt off is the pulley loose? Does it make noise when you turn it by hand? Notchy grabby or geared feeling?

Call Dan and see how much a new clutch is and/or are separate parts like the bearing are available. On other vehicles you need a press to replace the bearing, not sure on the cruiser. IIRC they were sealed permanently lubed bearings if a new clutch is expensive and you cannot get the bearing you may have want to get access to it and take it to bearing house and see if they can get it, since the AC has its own belt you should be able to remove the belt and clutch and still drive, usually you can remove the clutch without loosing the Freon charge, the seal is usually on the input shaft.

Hopefully someone like JDay that has actually worked on a cruiser clutch can confirm.

 

[flintknapper]

Yes, under the Compressor On-Vehicle Inspection - Magnetic Clutch section, it has a visual inspection for grease at the clutch bearing, and it says inspect Magnetic Clutch Bearing for noise... start engine, check for abnormal noise from near the compressor when A/C switch is off. If abnormal noise is emitted, replace magnetic clutch .

A little odd to me.. if I go out and start it up right now.. no noise. Turn the AC on then off... noise.

In the 3-D blowup sketch, it list three things as part of the magnetic clutch... pressure plate, rotor, and stator. It doesn't specifically list bearing. Do you know if the bearing is inside either the rotor or pressure plate?

I'll inspect closer for grease. I'm also going to double check the belt tension to be for sure.

Thanks,
Rookie2

Check all of the mounting bolts to make sure you're not getting vibration induced "clutch chatter".

Next remove the electrical connection from the Stator(coil) and check with a VOM to make sure that there is NO voltage when the switch is turned OFF. Next, remove the V-Belt and spin the rotor by hand, listen and feel for any roughness in the bearing (it should free wheel with little effort and little to no noise).

If everything is good to this point then it pretty much points to the pressure plate. Take a feeler gauge and check between the pressure plate and the rotor and see that you have .020 to .030" gap between them.

If your gap is correct then my guess is the spring arms on the pressure plate are worn and are vibrating..... (sounds like hissing/or cymbals) "clutch chatter".
Engine vibration is enough to cause a worn pressure plate to give off a chattering sound. It won't (can't) do it when engaged unless you have a weak stator.

Check these areas and let us know.

There are other procedures for checking the stator (coil) etc... but start with these and see what you find.

 

[Rookie2]

Great feedback guys, thanks for the help. When I went home last night and did the AC on/off thing, I didn't here the metallic hiss as I have on previous occasions. I must say, I don't run my AC very much. Just on the occasion that I'm out during the day and it's really hot out. I do try to turn it on from time to time just to keep eveerthing circulating, but in the winter I may not for a couple of months at a time. I will try some of the other suggestions you all have given to see if anything shows up. Probably by Wednesday night before I can get the belt tensioner.

Raven: Metallic hiss may not be the best descriptive. I may need to hear it again, and think about how best to describe it.

Thanks again,
Rookie2