[parsonsj]

Originally Posted by John

If the V/A (or ISIS) controller manages the compressor, then there must be a sensor to know when to turn off the compressor when liquid side pressure gets too high. So we're back to a trinary switch (maybe just a binary switch?) to do that -- negating one of the key advantages of having the ECM manage the fan. I suppose it's still better for the ECM to manage the fan (does it soft-start the fan to reduce inrush?), but this hybrid system will have two pressure sensors that aren't integrated.

I'm going to talk to ISIS about their V/A controller and whether or not it can be modified to support the CAN-bus protocol to be able to talk to the ECM. I'm sure Jay's question will be: what is the CAN-bus sequence to tell the ECM to enable the A/C clutch?

Edit: I realize that just the CAN-bus electrical connection isn't enough. GM has a proprietary protocol that would have to be reverse-engineered to get this to work. I also asked ISIS about their ability to read CTS and A/C sensor data and manage the fans. I'll report back.

Here's the report back from ISIS:

Originally Posted by Mike from ISIS

We do have a J1939 interface on a version of the Mastercell but that is only to read PGNs sent to the Mastercell by other devices (We buy switch packs that communicate J1939) and does not send commands out at this point. The GM ECM would have to communicate using standard J1939 which I don't think it does and we would have figure out how to send the proper commands over the J1939 bus.

So does anybody know: does the GM E67 use J1939 protocol over CANbus?