[s-cars] AC low side recharge adapter

[Tom Green]

This issue has been revisited many times without any definitive  
answers given to the list.  The most
often asked is about adapting a gage set to the low pressure port for  
a DIY recharge.  But no one
has offered any specific details for this even if they said " I did  
this myself".  Even the local dealer
service manager claims they never use the low pressure port, only  
connect to the high pressure
port at the condenser, evacuate and refill a measured charge with the  
engine off, and measure the
high side pressure and interior duct temperature for any fine tuning  
of the charge with the engine
running at 2K rpm.  There is some risk of introducing liquid  
refrigerant into the compressor by using
the low side port if you are not careful or overcharge the system  
even though shops use this system
on most vehicles, and of course, the high side pressure will burst a  
DIY can and will only allow a
recharge with the compressor off.

My high side valve is on the front right side of the condenser and  
easily accessible on the S6.  I don't
know about the R12 systems on the S4.

Is there someone on this list who can put these issues to rest?    
That is, can someone provide a source
for a low side adapter?  Does anyone have specific details of the  
differences in the URS4 systems using
R12 and the URS4/6 systems using R134a?

Tom


> Date: Mon, 02 Jul 2007 21:24:49 -0400
> From: Kent McLean <kentmclean at comcast.net>
> Subject: Re: [s-cars] AC low side recharge adapter
> To: s-car-list <s-car-list at audifans.com>
> Message-ID: <4689A561.5060607 at comcast.net>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Aaron Ryba wrote:
>> Like others have mentioned I took off the low pressure switch (F  
>> 73) located in
> the right
>> plenum and planned on filling her up there however it seems like  
>> the threaded male connection
>> with the schrader valve there is a metric 10 mm thread size which  
>> won't work with anything
>> I can get at Autozone or Advance Auto parts. I am trying to avoid  
>> spending $100 bucks on the
>> high end manifold gage set or paying a shop $120 to fix it for me.
>
> I'm almost in the same boat.  With 3 Audis with weak or no AC, I  
> thought
> I'd be better off investing in the equipment and doing it myself. I  
> bought
> the not-quite high-end manifold gage set ($60 at Robbins, a  
> supplier to
> mechanics in S. NH, not the $39 set at the local national consumer  
> chain.
> Plus another $30 in the R134a-specific hoses.). I bought the R134a  
> adapters.
> I haven't gotten around to actually doing the conversion(s) yet.   
> But my
> understanding so far is that the gage sets needs to tap into both  
> the high-
> and low-pressure sides of the system, so you still need to have  
> access to
> a low-pressure side valve.
>
> My am also under the impression is that the valve on the compressor  
> is meant
> to drain the oil from the compressor, but as it is on the low- 
> pressure side,
> -- and here I'm not 100% sure/convinced -- it can be used to  
> recharge the
> system. I'll leave it to someone with more experience to confirm or  
> reject
> that idea.
>
> -- 
> 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