[Vwdiesel] A/C

[Val Christian]

Shalyn,

There are fundamental measuring points on AC work:

-ambient air temp
-exhaust air temp
-condenser temp    
-engine RPMs  -> compressor RPMS
-compressor low side PSI
-compressor high side PSI
-visibility of fluid/foam/nothing(visible) in sight glass
-condenser fan on/off or speed
-cabin fan speed

So if you are going to describe a problem, couch it in these attributes
for the best response.

If I read what you have written properly, you have verified that the clutch 
for the compressor is actuated, and the compressor (not just the outer pulley
for the compressor) is turning.  The system is not cooling air, and your low
side is 95 psi and the high side is 110.  

I would interpret this to be a sign that the compressor is incapable of 
creating a significant "head" of pressure of the coolant.  There are several 
reasons why this could be, but the most likely is the compressor has failed.

If the compressor has failed, and I haven't said that it has, simply 
replacing the compressor may be ill-advised.  Failed compressors tend
to leave all kinds of debris in the coolant loop, which can rapidly 
accelerate the replacement compressor's demise, and can block important
things like expansion valves (H blocks in some vehicles).

So, to diagnose to the next level, as you turn the compressor on and 
off, is the clutch fully engaging (visual inspection) and is there any
sign of slippage.  When the engine is off, how does the compressor feel
when you turn it over?  You can do that with the belt on, and the 
clutch disengaged, and of course, the engine off.

If you listen as the compressor engages, does the engine RPM momentarily 
drop, as if there is a substantial load on the engine?  Does the compressor
make hideous noises like a blender running at high speed with a bowl 
of nuts and bolts?

Report back, and I will do my best to get you to the next step.

For everyone's curiousity, I'll make up possible answers for a worn, but 
servicable VW AC.

inlet compressor: 28 psi
outlet compressor: 220 psi
outlet cabin air, full fan, recirc on: 36F
ambient air: 78F
condenser temp (passive IR radiometer "laser thermometer") : 190F
condenser fan : on
sight glass : fluid with very small bubbles sometimes moving by
engine RPM (TDi) : 910, with clutch fully engaging
compressor noise : audiable cyclic noises from compressor, no grinding noises,
no hammering noises, and cyclic noise intermittently stops upon disengagement 
of compressor, which intermittently happens as the outlet air drops towards 
32F
drain from evaporator (near heater coil, in cabin blower area) : drippage of 
condensed water on the ground.

Hope this helps.

Val











Ie's finally getting hot enough here in Texas that I'm finding motivation t=
o fix the air conditioning on my '00.=A0 I came up with a used set of gauge=
s, hooked them up, turned on the a/c and got 95 & 110 psi low/high.=A0 Zero=
 cooling in the cab.=A0 The compressor is turning, but I'm guessing it's ju=
st for show.=A0 While I have a pretty good theoretical understanding of how=
 it works, I thought I'd run it past some of y'all that have actual practic=
al knowledge.=A0 My assumption is that there's about to be a compressor-siz=
ed hole in my bank account.

-Shalyn

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