Warning to those of you using AC pressure input for WB signal

[5_Liter_Eater]

This may be '05 C6 specific but the other day I was sitting in the garage doing some idle tuning, I had the AC signal bypassed with the WB signal, just sitting there idling. The idle started to hunt only with the AC on (due to the compressor loading up) and then I hear a loud hissing sound from under the hood. The over-pressure pop-off valve on the compressor opened! I believe the release was due to the system being overfilled from the factory. There is a TSB on the '05's and early '06's regarding over-filling. They used to fill the system to 1.4# of R134 but numerous complaints about the AC not working well in hot weather made GM realize that it should only be filled to 1.1#. Systems were engaging the AC pressure safety system and the compressors would not cycle. I had noticed that my AC was not working well ever since it started getting hotter.

Anyway, since my PCM wasn't seeing the AC pressure it couldn't kick off the compressor. Lukily the system had a pop-off valve or it would have seized up the compressor or created a leak in the system to vent the pressure. So if you're doing this, be careful to turn off your AC when tuning...

[cgoodwrench]

I had a similar prolbem, i put e-fans on my truck and without any airflow across the condensor my ac pressure was rising over 400 Psi. so I had to add a relay to kick the fan on when the compressor engage's. Did you notice that your fan was running with the compressor engage, I think on some GM's the fan is wire to the high pressure switch and will turn on the fans at a certian pressure, hope this helps

[Nitrous]

Thank god for cigarette lighter power supplies! That sucks but you had the pop off valve. Good info!