Air conditioning compressor clutch assistance requested

[Seaaggie]

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?

 

[S]

Hi Seaaggie!

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.

I'll happily share what little I know about these.

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.

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.

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.

Just one wire on these IIRC, +12V engages the clutch.

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.

Again? And with the same brand of aftermarket 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.

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.

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?

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.

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?

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

 

[Edward Hayes]

I was under the impression that the AC clutch usually does not come
with the compressor. Maybe the original clutch was transferred to the
replacement? In any case it is not unusual for a reconditioned
compressor to give up soon unlike a "rebuilt" compressor. In an R134
system the center vent tempeture should be ~35 degrees F. below the
outside temp when the engine is running at 1500 rpm. Car windows open,
fan on max and not recirculation mode. ed