So I have been trying to nurse my a/c back to health... compressor changed, o rings replaced, full a/c charge, clutch engages off a 9V battery and a/c will run cold, evaporator will go sub 10 degrees no problem. With the regular electrics connected then I can see the a/c request kicking in within a few seconds of ignition start (nanocom, read from the ECM). I can also toggle the a/c request on and off with the a/c switch, so the nano reading is good, and live. Request is an active-low 12v connection.
The A/c grant is 5V, also active low. As far as I can see I don't get the grant back from the ECM - does anyone have the exact GEMS criteria for grant? BBS talks about temperature, load and acceleration... but what specifically? The nanocom HEVAC connection is pretty unreliable once the car has started (it says it can't connect, but still reports most input variables), but it reports no grant. When I have time I will pull the ECU and confirm that by testing the pin. I tend to believe the nano for now re lack of grant, but not 100%. Because the grant is active low then there can't be a wire break
As a plan B I was thinking to join the A/c request output from the HEVAC, via a 5V regulator to the a/c grant input to the HEVAC - then they would both go active low together automatically, and would be 12v/5v inactive....would this do as a work-around?