My 1998 Subaru Outback 2.5L has an air conditioning problem and I'd like to see if any of you brilliant people could offer some advice. About 10 months ago the original compressor was replaced, as the mechanic said it was dead, with an aftermarket compressor. Shortly thereafter the compressor clutch started making a squealing noise each time the clutch disengaged, this wasn't a belt noise, it was actually coming from the clutch.
I disconnected the power supply to the compressor and the noise was very loud. The clutch seemed to be still trying to turn with the belt but there was no power to the compressor. When the clutch was engaged the unit seemed to work great. Cold air was abundant. However, I took the car back and the mechanic replaced the compressor.
A month went by and the same sounds returned. Fed up with the mechanic, I've put off any thought of taking it back to him.
Could the clutch be too close to the pulley assembly and it's being caught on the pulley when disengaged? If so, is it possible to remove the clutch and sand it down or something?
The other problem is cooling while not moving. The vehicle doesn't seem to cool at all unless it's under way. Any ideas on this trouble?
I'll happily share what little I know about these.
Hmmmm. Not a squeal when it engages? That would be the usual issue, and is normally addressed by tightening the belt, or installing a new one. I have seen the idler bearing in the compressor clutch become noisy; the sound could be described as a "squeal" I suppose.
Just one wire on these IIRC, +12V engages the clutch.
Again? And with the same brand of aftermarket compressor?
If there's systematic problem with the aftermarket parts he's installing, he will probably appreciate knowing about it. I'd definitely run it by him again; it's not your fault it's making noise, and in all likelihood, not his either, at least not directly. Ask him to find an OEM compressor from a salvage yard (~$75), rather than installing another aftermarket item if it comes to that.
I've never attempted to disassemble one of these, but it might be worth a try if all else fails. Before you go to that extreme, tho, try this: Remove the drive belt and work the compressor pulley by hand. It should turn smoothly with virtually no effort. If there is drag present, if the inner part (the compressor input shaft) is trying to turn, or if you detect any sound at all coming from the idler bearing as you spin it, the compressor is bad. As in warranty.
That's truly odd. If the engine is running, and the compressor is engaged (inner part is spinning; have a look to be sure), you're gonna get cooling, kinda has to be so. IIRC, that is how they test the AC; car idling, AC on MAX, temperature probe in the center vent, AC should cycle off when the air temp reaches 39-40 degrees, and back on at
45ish. FWIW, the ECU will also cycle the AC under some conditions; heavy load on engine, defrost on, who knows what else. Use a jumper wire to power the clutch directly from the battery if in doubt.
You might also have a look at the idler pulley that adjusts the belt tension; these are notorious for causing objectionable noise, but generally the noise is always present when the engine is running. Same rules as the idler in the compressor; anything other than effortless and silent rotation is bad. A mechanics stethoscope may help you isolate the sound. They are cheap enough ($5-$10) that you might want to pick one up before you try anything else, just so it's at hand.
ByeBye! S.
Steve Jernigan KG0MB Laboratory Manager Microelectronics Research University of Colorado (719) 262-3101
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