41v

97 A4 2.8 Q 160k
ac blows warm air

compressor turns on, stays on ok when switched on, does not cycle

manifold gauge set reading was fluctuating on low side 25-30
so I added 2 cans of 'ez chill' r134 with oil/dye/sealer
r134 low side went to 30 steady
high side stayed at about 125 before and after

low side pressure never drops so doesn't seem like a leak anywhere

when car is turned off, I hear a very slight momentary release of air pressure somewhere around the evaporator, is that normal?

low side doesn't go past 30, do I need another can? I would like to see 40 low and 200 high (85 outside now)
any typical parts/switches/sensors to check?
would VCDS-lite indicate any issues?
should I evac and recharge from scratch?

Prospeeder

its low on refrigerant. You need another can or so. High side should be about 220-250 if its rather hot out. If you have added the full amount and its the same. Remove the orifice tube and inspect or replace it. It can block up and cause a low low side and a low high side reading.

41v

good call, thanks.. ac now blowing 42 degrees after another charge of a 12oz can, cheap stuff no frills/oil/dye just R134

so that makes 2 cans of 18oz with dye/oil plus 1 12oz can of straight refrigerant, was concerned about over charging but guess not.

Those cans with a push-button/built in gauge seemed to leak a bit while charging, maybe a lot actually. This time I got a can-piercing adapter to be able to attach a regular can to the yellow line, and was a much more solid hookup and dispense compared to the push-button cans.

the manifold gauges didn't change much but after low side hit steady 30, the compressor sounded slightly lower-pitch hum as the refrigerant was reaching it and noticed the ac lines getting cold and moisture appearing.