[Vwdiesel] A/C

[Tad]

Not that I know a lot about AC, but don't the 00's have the
variable-displacement compressor?  I know my 01 does.

On Fri, May 6, 2011 at 8:58 PM, Val Christian <val at mongo.mongobird.com>wrote:

> 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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