[s-cars] An A/C question

[Djdawson2 at aol.com]

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My A/C is actually working fine (a 134a system, 93 S4)... however, out of
curiosity, I was going to measure my high and low side pressures, and see if the
charge was up to snuff.  Interesting thing is, I can't seem to locate a low
side port.  The high side is clearly accessible on the passenger side of the
condenser, but in tracing the low side line from the evaporator down along the
firewall, into the engine compartment, through the dryer and back to the
compressor, I see no low side port.  Am I missing something here, or is the low side
port located behind the cash register at my local Audi dealer?
Thanks,
Dave in CO