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.....
VY LS1 A/C Wiring - Custom Setup
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pman92
- Posts: 470
- Joined: Thu May 03, 2012 10:50 pm
- cars: HZ One Tonner
VE Ute - Location: Castlemaine, Vic
Re: VY LS1 A/C Wiring - Custom Setup
Originally the BCM / ECC module would signal the PIM via ALDL the AC Request.
Not sure how it works after the PIM, but I would assume it just passes that information on via VPW - there wouldn't be a separate wire for AC request.
Red 18 is the feedback to PCM to show the clutch is engaged.
Haven't got a diagram on me, but I'm assuming the other wire your talking about (red 43?) would be the output from the PCM to switch on the AC relay.
There is definitely a relay, the PCM doesn't power compressor directly
Not sure how it works after the PIM, but I would assume it just passes that information on via VPW - there wouldn't be a separate wire for AC request.
Red 18 is the feedback to PCM to show the clutch is engaged.
Haven't got a diagram on me, but I'm assuming the other wire your talking about (red 43?) would be the output from the PCM to switch on the AC relay.
There is definitely a relay, the PCM doesn't power compressor directly
Re: VY LS1 A/C Wiring - Custom Setup
No worries.
Sounds like it's easier to just bypass BCM all together and run a new circuit and relay direct to PCM EVAP and compressor.
Sounds like it's easier to just bypass BCM all together and run a new circuit and relay direct to PCM EVAP and compressor.
Re: VY LS1 A/C Wiring - Custom Setup
So My new #6 join with thr R12 thread for the sensor to attach arrived and the sensor is a different thread/size.
I'm going to bypass the sensor entirely and just use the EVAP switch to turn everything on.
Am I correct in that as soon as the PCM detects the clutch is on it will assume the a/c is on regardless of reading from the sensor? (i.e. if the sensor doesn't have a reading it just won't ground Red#43), but Red 17 and red 18 get a 12v signal from the switch that also turns the relay on for the compressor clutch and a/c fan?
I'm going to bypass the sensor entirely and just use the EVAP switch to turn everything on.
Am I correct in that as soon as the PCM detects the clutch is on it will assume the a/c is on regardless of reading from the sensor? (i.e. if the sensor doesn't have a reading it just won't ground Red#43), but Red 17 and red 18 get a 12v signal from the switch that also turns the relay on for the compressor clutch and a/c fan?