[V6-12v] AC running not so cold

[Wilfried Link]

If your 94 is like my 95, the only actual low pressure
service fitting is on the compressor's outboard side.
I have had my car serviced through the high pressure
fitting on the condenser (easily visible on the right
side of it when you open the hood) by a local
Firestone shop and it worked wonderfully for three hot
seasons. I have also had it serviced through the low
pressure switch port right on top of the evaporator
under the right windshield wiper. The switch is easily
unscrewed, and won't expel refrigerant because it has
a Schrader valve under it. The technician I worked
with used a hose from an older servicing system that
screwed right onto that fitting. R134 wouldn't flow in
until I figured out how to use a tiny Schrader valve
spring as a way to depress the Schrader pin on the
fitting (duh!), the way a normal, industry-standard,
blue-capped quick-disconnect fitting's pin is
depressed by the servicing equipment (or can) hose
connector. Unfortunately for me, that technician, who
had the afformentioned mysterious old hose in his
private stash, has moved away. And my AC is once again
very weak. And the weather is getting hot around here.
Blast! There are several adapters available online and
at auto-parts stores (the local Big-A has a few),
usually intended for Freon to R134 conversions. One
end is the standard R134, blue-capped, lo-pressure
quick-disconnect fitting, and the other is usually a
threaded female end for screwing onto the old Freon
fittings. I have yet to find an adapter that will fit
the Audi's low-pressure switch-cum-service port, which
is a M12x1.5 male. When I do, I'll have the problem
licked and let everyone know! Now that I think about
it, I may try and make one by tapping out its female
end to fit. Then it's just a matter of ensuring the
Schrader valve is opened by connecting the service
fitting, and carefully monitoring pressures. 

Cheers,
Wil
95 A6 Avant
 
--- Kent McLean <kentmclean at comcast.net> wrote:

> When I bought my '94 100 S Avant, the AC worked
> fine. It wasn't ice cold,
> but it was cold. Now, 3 years on, it doesn't blow
> cold, and summer is here.
> My new-to-me '91 200 20V Avant, on the other hand,
> didn't blow cold or
> even cool when I got it. So...
> 
> - Is there a good on-line tutorial for how
> automotive AC works?
> - Does my '94 have a low-pressure valve for adding
> R134a? (I know
>   some Audis only have a high-pressure valve.)
> - I don't know that the '91 has been converted to
> R134a. Will a
>   cheap R134a conversion kit let me use R134a? Or do
> I need to
>   change things (hoses, compressor, etc.)?
> 
> The '94 is a non-automatic climate control. Yup, it
> has 3 big
> old-fashioned knobs :) So debugging its system using
> the CC
> won't work there.
> 
> Thanks,
> 
> -- 
> Kent McLean
> '91 200 TQA #1, for sale
> '91 200 TQA #2, no name yet
> '94 100 S Avant, "Moody"
> '89 200 TQ, "Bad Puppy", up in smoke
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