[s-cars] A/C shutting down

[Tom Black]

Doesn't the Audi climate control system only activate when the coolant temp
reaches a certain value. I know this to be true for sure in cooler temps.
???
Tom
----- Original Message ----- 
From: "Bob Rossato" <bob.rossato at att.net>
To: "Mike Claire" <mclaire_us at yahoo.com>; "TOM GREEN" <trgreen at comcast.net>;
<s-car-list at audifans.com>
Sent: Saturday, July 24, 2004 8:19 AM
Subject: RE: [s-cars] A/C shutting down


> I'm not so sure it's the engine overheating as much as the AC system
> pressures being high, or at least the sensors thinking it's high.  The
> engine cooling system on these cars is more than up to the job.
>
> I too have had the AC shut down on me, but only when first starting the
car
> after it's been sitting in the parking lot on a hot day.  I've had it
happen
> a handful of times when going out for lunch.  Ambient temps are typically
in
> the mid-90s and up.  AC will shut off a few seconds after I start the car.
> Immediately pushing the AC button does nothing.  Continue on and try AC
> button again after 30-40 seconds and it starts back up but then shuts down
> after a few seconds again.  Repeat wait cycle and this time it holds.  By
> the time I'm out of the parking lot it's holding and never acts up again
for
> the rest of the trip.  I've never had to drive the car in stop and go
> traffic so I don't know if it would start acting up again in that
situation.
>
> >From my review of the Bentley manual a while back on this issue, I found
the
> following three sensors that would shut down the compressor:
>
> F73 A/C Refrigerant Low Pressure Switch - Switches A/C clutch OFF if
system
> suction pressure is too low (low refrigerant charge)
>
> F118 A/C Refrigerant High Pressure Switch - Switches A/C clutch OFF if
> system pressure is too high
>
> G111 A/C compressor Speed Sensor - Determines A/C compressor speed;
compares
> compressor speed to engine speed and calculates belt slippage and switches
> compressor OFF if slippage is too large (for example, if belt is too
loose.)
>
> Since I'm just starting the car after it has been sitting for 4-5 hours,
> engine temperatures are not an issue in my situation.  I think it's just
the
> high pressure switch on the AC system that is doing it.  Whether it is
> because the pressures are truly high and the system is trying to protect
> itself, or the high pressure switch is just overly sensitive I don't know.
> But my money is on the latter.  Sensors do drift with age.  That in
> combination with the higher baseline pressures as a result of the car
baking
> in the hot sun could be enough to trigger it.
>
> Might be worth changing that out and see if you continue having problems.
>
> Bob
>
> > -----Original Message-----
> > From: s-car-list-bounces at audifans.com
> > [mailto:s-car-list-bounces at audifans.com]On Behalf Of Mike Claire
> > Sent: Friday, July 23, 2004 6:50 PM
> > To: TOM GREEN; s-car-list at audifans.com
> > Subject: Re: [s-cars] A/C shutting down
> >
> >
> > Thanks Tom and other listers who replied.  In a
> > perverse way I guess this is good news - nothing to
> > fix!  But it still surprises me that a car can be
> > designed without sufficient cooling to survive in even
> > 110 deg temps without having to resort to shutting
> > down A/C.
> >
> > One more question about these A/C systems.  The
> > compressor is LOUD.  A constant groan kind of like a
> > dry power steering unit.  Is this normal too?  I guess
> > I hope it is...
> >
> >
> > Mike
>
>
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