[s-cars] A/C recharge

[Thomas R Green]

There is too much controversy on self-service for the a/c system to do  
a FAQ entry.
And, all the questions were about the R12 system which I do not have  
and do not
intend to research.

I did find a tank adapter for R134a that will connect to the low  
pressure port to allow
a top off from a 12 oz refrigerant can.  I bought mine at Midway  
hardware (online) and
cut a small piece of brass rod so the schrader valve on the adapter  
would actuate the
schrader valve below it when the tank was attached.  That will work  
with the system
running by slowly adding refrigerant.  I use a gage set if I am doing  
this, and I only
used it a couple of times.

It depends on what you have in mind to do.  Are you opening the system  
anywhere
to replace anything?  Has the system been operating well and just  
slowly lost the
charge (you think) over several years?  What did you want to do to the  
system -
just throw some refrigerant in the system and see what happens?  You  
can do that
but it will leave any moisture in the system that has crept in through  
whatever leak
the freon went out.  The system will have high pressure in parts and  
low pressure or
vacuum others that allows stuff to leak out and leak in at the same  
time or place.
Moisture is not good with pag oil, and you will pay the price if you  
do this too much.

The correct method you allude to is through the high pressure port on  
the left side
of the condenser.  You find and fix the leak and then evacuate the  
system with a
vacuum pump.  Then connect a refrigerant tank and measure in the  
correct amount
of refrigerant by weight with the a/c off.  This will pressurize the  
system to around 100
psi with the compressor off, which is why you can't use 12 oz cans  
here even if you
could find a way to connect them, and around 300 psi with the  
compressor on.

You do agree that you don't want to pressurize a small can of  
refrigerant to 100
psi with your body in close proximity, don't you?

If you already know all this, you can probably do it yourself.  The  
gage sets have
been selling at Harbor Freight for $29 or you can "rent" them from  
Auto Zone or
other FLAPS for free and the vacuum pump free rental also.  The hard  
part is
charging it with the correct amount of freon.  Oil is another story,  
and probably
not a concern if the connections don't show evidence of oil leaks and  
nothing was
replaced in the system.  Then you could just use the R134a with make- 
up oil  in
the can.

If you do not do this yourself, the dealer is not necessarily the  
place to do this.
A good automotive a/c shop should have no problem with this.  Even  
most Firestone
stores have a computerized a/c service cart to measure the charge  
after it
evacuates the system.  How much leak detection and repair must be done  
first
depends on the area.

Tom


> -----Original Message-----
> Date: Fri, 2 Apr 2010 15:13:13 -0600
> From: J R <audiurs4 at gmail.com>
> Subject: [s-cars] A/C recharge
> To: s-car-list at audifans.com
> Message-ID:
> 	<u2p2e10b5e81004021413kfd93a3faw853aa56d4098200 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> My 93 URS4 needs an A/C recharge.  Does anyone have a procedure for  
> doing
> this?  Can I do it myself?  I've read emails to this list and posts to
> forums where people say no because it doesn't have a low side charge  
> port.
> I've read other emails on this list and other posts where somehow  
> people did
> it anyway.  I pride myself in not having had to take my car to the
> stealership since I bought it.  I've done all of the work myself.   
> Is there
> any way to recharge/re-oil the A/C on a URS4 yourself?
>
> Thanks,
>
> JR