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Davidf · 09-27-2021, 10:40 AM

I still think a lot of functionality is missing. With this (above) wiring diagram, ECM control of the compressor is not present. Why not some form of:

A/C on/off from fan switch ->HP cutout on back of compressor ->ECM pin #17 (a/c request).

ECM pin #43 (ground output) -> compressor relay -> compressor

a/c LP cycling switch (or trinary switch, low side, I suppose) -> ECM pin #55

Condenser fans can be triggered by the compressor relay above so they come on whenever the a/c is on...good practice. Or, you can use fan 1 or 2 output from the ECM. Tell your tuner to trigger the fan output with the a/c request.

09-27-2021, 10:40 AM	#5
Davidf Registered User Join Date: Nov 2014 Location: Austin Posts: 749	Re: AC compressor relay and Trinary switch wiring question I still think a lot of functionality is missing. With this (above) wiring diagram, ECM control of the compressor is not present. Why not some form of: A/C on/off from fan switch ->HP cutout on back of compressor ->ECM pin #17 (a/c request). ECM pin #43 (ground output) -> compressor relay -> compressor a/c LP cycling switch (or trinary switch, low side, I suppose) -> ECM pin #55 Condenser fans can be triggered by the compressor relay above so they come on whenever the a/c is on...good practice. Or, you can use fan 1 or 2 output from the ECM. Tell your tuner to trigger the fan output with the a/c request. Last edited by Davidf; 09-27-2021 at 05:30 PM.