Anyway to bypass A/C to run a toggle "high idle" switch for PTO??

[relentlesshustler]

I'm looking to run a toggle switch for "high idle" that will tell the PCM that the A/C is on(not currently running A/C). I have read that it will not work without pressure sensors and I've also read that it may be possible to wire up resistors but the instructions were unclear. I have an LQ4, harness, and underhood fuse block from a 2003 Chevrolet Express. Donor vehicle is a Square Body car carrier. I understand I'm not inventing the wheel here and a link to the answer would be greatly appreciated!!

Eric

[Jeff7577]

The pressure sensors are just switches. You need to ground the low pressure signal and the high pressure(a/c request) will be your enable with 12 volts. ac.jpg

[clshortt1]

I would think you would have to emulate the AC request signal that would normally come from the HVAC control head. Then the ECU would see an AC request signal and jump to the idle w/AC on tables. I'm not sure that using the AC pressure sensors would get you anywhere. The ECU has to see an AC request.
I think the ECU just ignores the pressure sensors until it sees and AC request.

[Jeff7577]

I would think you would have to emulate the AC request signal that would normally come from the HVAC control head. Then the ECU would see an AC request signal and jump to the idle w/AC on tables. I'm not sure that using the AC pressure sensors would get you anywhere. The ECU has to see an AC request.
I think the ECU just ignores the pressure sensors until it sees and AC request.

Yep, if you look at the picture I posted the request comes from the control head and passes through the high pressure switch if it?s closed.