|Tech Article Title
A/C Recharge (R-134a)
I asked a few times about recharging our own air and got a
few mixed answers. Although on some A8s and earlier Audis it could only be
refilled on the high side by a dealer, we can do it ourselves with the $25 kit
from Wal-Mart. If you know what you're doing, this answers the age-old question,
and you're set.
For those wanting more info, here is a quick "step-by-step" ... I
figure with all the great info I get here and tutorials I've read, it's time I
First, remove the plastic at the top of the engine bay. The same plastic that
has to come out to swap out your ECM. Mine only seems to be secured by the
weather stripping at the top of the engine compartment. I pull that out, and I
can slide out the plastic without issue.
Once that's clear, approach the car from the passenger side. You'll see metal
lines running back into the cockpit from the engine compartment, right by the
negative battery cable. Each of those lines has an access valve. One is too wide
for the recharge kit hose, the other valve is the correct size. They should both
have a plastic cap, although only one of mine did. In my 2000 S4 the inside hose
is the low-pressure line which we hook into. The low-pressure line is the fatter
of the two.
Pop off the cap and hook up the pressure tester. See what it reads, just for
grins. Don't hook up the refrigerant can yet! The way my kit worked is there is
a pressure tester with two hoses. One hooks into the AC, the other has a valve
which goes into the R-134A can.
Turn over the car. Kick the AC temp on "low" for the temp and crank
the fan all the way. Make sure the compressor engages; you'll hear it drag on
Once you know the compressor is on, hook up the R-134A can. With the kit I had,
you had to puncture the can with a twist-screw that was a part of the valve that
hooks into the pressure tester. Once you screw it all the way in, you have to
unscrew it a few turns so the refrigerant can escape from the can. You should
see the pressure tester rise. The "safe" range on kit I had worked
well. I went to the 'max' of the "safe" range. Whatever that was.
Sometimes the valves on these kits are cheap. It may twist on, depending on the
kit. You may need to hold the valve onto the low-side AC port to make sure it
engages. I did this with my kit when I realized it was a POS kit and it did
charge, but by the time I realized I had to hold it down, there wasn't enough refrigerant
left for it to charge. My neighbor saw what I was doing and has a full
mechanic's kit (with low and high side tester, etc) and a 30lb bottle of R-134A.
The valve on it is a standard recharge valve, and it plugged right into the
low-side port. Being a professional kit, it fit well, and he was able to top off
my charge. So I lucked out in my quest to charge my AC.
The moral is, a generic recharge kit will work. Make sure when you recharge you
don't use just raw R-134A. Make sure you get a can that includes the lubricant
additive, which keeps the system oiled.