PWM cooling fan(s) control using ECM

[Vince@Meanstreets]

Originally Posted by samckitt

Is there a preferred position where the AC pressure switch needs to mount? Between compressor & evaporator, evaporator - condenser, or condenser - compressor?

anywhere between the condenser and evaporator. #6 line

[65C6Corvette]

Originally Posted by Vince@MSperfab

anywhere between the condenser and evaporator. #6 line

Thanks,

This is helpful. Where did you install the trinary switch? Assuming that you also used it for the vintage air.

[parsonsj]

Where did you install the trinary switch? Assuming that you also used it for the vintage air.

You don't want to use a trinary switch when the fan is being controlled by the ECM. You should use a binary switch to protect the compressor from over/under charge since the ECM doesn't control that.

[Vince@Meanstreets]

Originally Posted by 65C6Corvette

Thanks,

This is helpful. Where did you install the trinary switch? Assuming that you also used it for the vintage air.

I usually put it right into the drier. But if I can't inline on the high side hidden in the fender.

Originally Posted by parsonsj

You don't want to use a trinary switch when the fan is being controlled by the ECM. You should use a binary switch to protect the compressor from over/under charge since the ECM doesn't control that.

Yes, there should be an AC input wire right? Let me see if I can find the pin #

[parsonsj]

Originally Posted by Vince

Yes, there should be an AC input wire right? Let me see if I can find the pin #

On the E67, the A/C request signal is via CAN request from the BCM, not a signal wire.

[Vince@Meanstreets]

Originally Posted by parsonsj

On the E67, the A/C request signal is via CAN request from the BCM, not a signal wire.

ECM fan request pins are a grounding circuit right?

[samckitt]

Originally Posted by parsonsj

On the E67, the A/C request signal is via CAN request from the BCM, not a signal wire.

So with the GMPP controller (I believe it is an E67), there is no point adding the AC pressure sensor/switch? Unless the BCM is added?

[parsonsj]

Originally Posted by Scot

So with the GMPP controller (I believe it is an E67), there is no point adding the AC pressure sensor/switch? Unless the BCM is added?

It would be better if the A/C request went through the ECM so we could have compressor protection features (like RPM limit, WOT cutoff, overheating protection, etc.). But we don't, so all we get are fan control features via the A/C pressure sensor. Is it worth doing? I think so, but it isn't ideal, and the system needs a binary switch to protect the compressor since the ECM doesn't/can't.

If only Vintage Air or InfinityBox (nee ISIS) had support for GM's A/C CAN-bus request...