VY LS1 A/C Wiring - Custom Setup
Posted: Wed Apr 24, 2024 8:40 am
Hey All,
I'm just wanting to understand how the A/C Clutch is enabled on a VY comoddore.
I have "most" of the VY wiring including BCM, but would rather have the PCM control the A/C clutch and requests rather than BCM, as I'm not using the VY HVAC or A/C controls.
Instead I have VY 0411 Engine harness, VY radiator 2 fans, and a universal EVAP unit. It just has a blower switch and I've wired in a 3 way switch for hot, off, cold.
When on hot the blower fans will start up and send 12v to the electric heater valve and open it up.
When on cold, the 12v is sent to the PCM on Red#18 to let it know that A/C is on.
Am I correct that the Red#18 is just letting the PCM know the A/C is running, or is it requesting the A/C to be turned on (i.e. send ground from Red#43 for the relay to be enabled?
My issue with the latter is it looks like the VY harness has a PIN that goes straight to the A/c Clutch 12v which means the PCM would have to send 12v @ around 20amp to kick on the compressor directly and would put a lot of load on the PCM yes?
Would Red 17 be the correct pin to use to connect to the blower fan switch when cold is requested, to tell the PCM, then use Red#43 to ground the A/C relay, and then have the 12v out put pin (87) connected back to Red!8 to tell the PCM the compressor is running?
In other words:
Red 17 gets told by 12v that the a/c is switched on.
Red 43 grounds the a/c relay to energise the relay to power the clutch
Red 18 receives the same 12v from the relay to confirm a/c is active
But it seems like the VY wiring is sneding direct from PCM to clutch for power on the diagrams I've seen.....
I'm just wanting to understand how the A/C Clutch is enabled on a VY comoddore.
I have "most" of the VY wiring including BCM, but would rather have the PCM control the A/C clutch and requests rather than BCM, as I'm not using the VY HVAC or A/C controls.
Instead I have VY 0411 Engine harness, VY radiator 2 fans, and a universal EVAP unit. It just has a blower switch and I've wired in a 3 way switch for hot, off, cold.
When on hot the blower fans will start up and send 12v to the electric heater valve and open it up.
When on cold, the 12v is sent to the PCM on Red#18 to let it know that A/C is on.
Am I correct that the Red#18 is just letting the PCM know the A/C is running, or is it requesting the A/C to be turned on (i.e. send ground from Red#43 for the relay to be enabled?
My issue with the latter is it looks like the VY harness has a PIN that goes straight to the A/c Clutch 12v which means the PCM would have to send 12v @ around 20amp to kick on the compressor directly and would put a lot of load on the PCM yes?
Would Red 17 be the correct pin to use to connect to the blower fan switch when cold is requested, to tell the PCM, then use Red#43 to ground the A/C relay, and then have the 12v out put pin (87) connected back to Red!8 to tell the PCM the compressor is running?
In other words:
Red 17 gets told by 12v that the a/c is switched on.
Red 43 grounds the a/c relay to energise the relay to power the clutch
Red 18 receives the same 12v from the relay to confirm a/c is active
But it seems like the VY wiring is sneding direct from PCM to clutch for power on the diagrams I've seen.....