Re: not enough A.C.

["Fred Munro" <munrof@isys.ca>]

Hi Ron;

    I'm not an expert on the A/C systems, but I've been through mine a
couple of times, so I'll take a stab at your question.
    Is your compressor cycling? When you turn the A/C on, the compressor
clutch should engage, turning the compressor. On a properly operating
system, the clutch will engage and disengage in a cycle determined by the
temperature in the evaporator core and controlled by the evap thermo switch.
    If your compressor is cycling and you are not getting enough cooling,
there are several possibilities:
    1. The freon charge is low due to other leaks. This is a distinct
possibility with the age of your car. I just changed a leaking compressor on
mine and now have to change the condenser and a high pressure line which
have just sprung leaks.
    2. The expansion valve is plugged with dirt which entered the system
when the compressor was changed.
    3. The shop put in too much oil when they changed the compressor
(unlikely but possible).
    4. The air flow through the evaporator is too low due to pluggage with
dirt or blower problems.
    5. The air flow through the condenser is too low because the rad fan
does not start when the A/C is turned on. This issue would resolve itself
when driving at highway speed.

    If the compressor is not cycling, there are another set of potential
problems.

    A. The freon charge is too low (see 1 above) and the low pressure switch
is open.
    B. The evap thermoswitch is defective. This switch is thoughtfully
placed right under the runoff from the plenum cover on the passenger side.
I've had to rebuild it on both my Audis due to contact corrosion. It's a
cool $450 at the dealer.
    C. Blown fuse
    D. Bad A/C control head.
    E. Any one of the system safety switches bad (low pressure cut-out, high
pressure cut-out, low temperature cut-out).
    F. Bad wiring.
    G. Defective compressor clutch.
    H. The dealer didn't put the v-belt back on (OK, I'm reaching a bit
here!).

    These are a few potential problems which come to mind and I'm sure there
are lots I've missed. The Bentley has a troubleshooting section on the A/C
system and you can work through it with a bit of patience.

Good luck!

HTH

Fred Munro
'91 200q  276k km

----- Original Message -----
From: Ron Wainwright <ron_01056@yahoo.com>
To: <quattro@audifans.com>
Sent: Sunday, July 04, 1999 8:54 AM
Subject: not enough A.C.


> I own a 87 5000sQ and just got A.C compressor replaced at dealer and
> charged ,(assuming that there were no leaks in the system) what should
> I check next? Any help would be appreciated.  E-Mail
> ron_01056@yahoo.com
>
>
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