[V6-12v] ac refrigerant question

[Tim Crift]

I have charged my '95 90Q through the high pressure port without difficulty.
The Bentley is necessary for this as well as a good set of gauges with an
integrated charge line.  No boiling of cans or the like.  Lookup the static
pressure that the system should have based on ambient temperature and fill
the system until the gauge reads that pressure.  The car should not be
running when you do this and it helps to keep the charge can upside down so
liquid Freon enters the system as it expands.

Tim

-----Original Message-----
From: v6-12v-bounces at audifans.com [mailto:v6-12v-bounces at audifans.com]On
Behalf Of Elliott Potter
Sent: Tuesday, March 30, 2004 10:21 PM
To: Edward Sluis
Cc: v6-12v at audifans.com; 'Jack Tozzi at Novi Cantori'
Subject: RE: [V6-12v] ac refrigerant question


Most other cars charge through the low pressure port.  I've never
seen a good explanation for why Audi decided to use the high pressure
port instead, except that it eliminates confusion over which system (R12
vs R134a) you have ... if you go to the car with your hose to plug into
the low pressure port, and there isn't one, you know you're on the wrong
track.

There is, in fact, a low pressure port - it's under the dashboard,
behind the climate control fan housing, on top of the ECU, and has the
low pressure switch screwed in to it.  To get at it, you need to remove
a kick plate, remove the ECU, then plug it back in sitting on the
floorboards (since the engine needs to run), then use a special tool (a
17(?)mm open-end wrench that's about 3" long) to remove the low pressure
switch.  Sort of inconvenient.

I've heard of people charging through the high pressure port using those
cans of R134a from a FLAPS (Todd?), but they boiled the cans first and
that would make me very nervous.  (I'm not an Audi engineer, but I did
take a class in thermodynamics my junior year at GT ... had I not
skipped most of them I might have a different view)

You can take your car to a decent shop and they
will have the proper equipment to fill the coolant and PAG oil through
the high pressure port (they don't top off through the low pressure
port).  If it's just low, they probably won't charge too much either.
Worth it IMO.
--
Elliott

On Tue, 30 Mar 2004, Edward Sluis wrote:

> Just a quick check, I'm not an Audi engineer, but I am an engineer and I'm
> just wondering:  You said that charging is suppose to be done through the
> high pressure port, as far as my knowledge of HVAC systems goes it is only
> recommended to charge through the high side with an approved charging
> station with the system off and then topping it off on the low side with
the
> system on.  If you're a do it yourselfer using the cans, your better off
> charging on the low side.  I may be wrong but that's what my experience on
> the design side of things seems to make me think.
>
> -----Original Message-----
> From: v6-12v-bounces at audifans.com [mailto:v6-12v-bounces at audifans.com] On
> Behalf Of Elliott Potter
> Sent: Tuesday, March 30, 2004 6:58 PM
> To: Jack Tozzi at Novi Cantori
> Cc: v6-12v at audifans.com
> Subject: Re: [V6-12v] ac refrigerant question
>
> On Tue, 30 Mar 2004, Jack Tozzi at Novi Cantori wrote:
>
> > Hello All,
> >
> > The AC in my 1995 Audi 90 is not delivering cool air this spring.  I
> haven't
> > done any troubleshooting to speak of but I can say that the compressor
is
> > not engaging when I hit the AC switch. This makes me suspect the low
> > pressure switch is being tripped.
>
> Very often under a low pressure condition the compressor will cycle on
> and off at least once when you turn it on, unless the pressure is
> *really* low.  You don't happen to have the automatic climate control
> (as opposed to the three knob system), do you?
>
> > My dilemma is I'm not sure which refrigerant the car is using.  It was
> built
> > in 06/94 but was in an front end accident prior to my purchasing the car
> in
> > 2001.  Because of the accident, the condensor has been replaced and I
> can't
> > find any other place where the refrigerant type is listed.  It seems
very
> > likely to me that the car has to have 134a because parts of the system
was
> > rebuilt because of the accident, but I'd obviously like to avoid
> > contaminating the system by adding the wrong refrigerant.
> >
> > So, does anyone know for sure what the car originally came with?
Bentley
> > was no help, it simply provided service info for both systems.
>
> Audi changed to 134a in October 1992, so you're sure to have
> R134a.  There should be a silver sticker on the back of the hood, on the
> passenger's side that says so.
>
> There's also no easily-accessible low-pressure port on the R134a
> systems; charging is supposed to be done through the high-pressure port
> on the front of the condenser.
> --
> Elliott
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