air conditioner - compressor or clutch?

I do not know how to tell if the symptoms I am having are
the clutch has failed or the AC compressor has failed or is about to.
This started a while back when the compressor would turn on and
sometimes I would hear a screeching sound that was brief at this
point I was seeing a 35 to 40 degree difference between outside
air and the vent temp on recirculate on fan speed 2.

One day the screeching rapidly became more consistant, every time
the compressor turned on it would make this sound.
I turned the ac off for 30 minutes and when I tried it again the
screeching sound
was longer and very consistant every time the compressor turned on.
The ac was still cooling but I would estimate only a 20 degree
difference.

I am thinking that the clutch is at the point where it is not able to
engage
properly and is slipping. But never having had a compressor or a clutch
fail before I don't know the symptoms of how either of these fail.

I would appreciate any help in how to distinguish. I have a shop lined
up that will
pull the r134a out of my system (had the conversion done a few years
back at a volvo dealer).
The car is a 1990 740 with the original compressor. I want to do the job
properly and
if the compressor is the problem I gather the system will need to be
flushed.
I have never flushed the system before and will have to find out what is
involved
to do this as well.

any help is welcomed
thanks
MR

 

[ ... ]

Checked the belt tension? A loose belt will slip and screech.


Gary

 

Gary,
I should have mentioned the belt tension looks good.
I watched the compressor kick in when all the noise happens
and the belt does not appear to be the issue.
Other thoughts welcome
MR

 

Mike,
I am leaning towards your suggestion of replacing the entire assembly of
compressor and clutch. Long ago I suspected an extreemly sloooow leak
in the front of the compressor. I assume a seal. Over the years there is an
oily residue in the belly pan which has gathered dust and debris from
driving.
I will look for iron filings in the pan as you suggest.

How does one determine if the compressor is failing and dumping particles
in the system?

Assuming it is the compressor, any advise on the best way to flush? Products
to use?
I gather the accumulator and the oriface tube must be replaced as these
will collect particles, if there are any. I am new to these steps.

Guess I am hoping the I got wise to this early enough that I don't have a
failed
compressor and all the junk in the system.

Other thoughts welcome
MR

 

Many Volvos use a Compressor drive belt that is very heavily loaded. If you use
a US spec. belt it will only work for a few weeks. The true metric belt has a
different contact angle than the "equivelent" belt that you buy at your local
auto parts store. This is one of the items I go to my dealer for. Of course you
could just over-tighten it and were out the clutch bearing.
Try belt dressing. If the squeel stops when you spray a little on the belt,
the belt is bad. Belt dressing won't quiet a clutch.

 

A lot of the stuff will collect at the orifice tube, simply because it
has a very fine screen to prevent the orifice itself from clogging. So
just removal and inspection by someone familiar with the system will
tell you if the amount of filings is normal or if the system needs to be
flushed. There are flushing chemicals available just for this purpose.
Keep in mind the more you dismantle the system the better the flushing
job will be, but the more likely you are to break some of your 13 year
old parts.