LS Swap A/C Questions

[Kiko_Jones]

Need help with the AC in my LS Swap. I installed a '99 Corvette LS1 into a 1996 GMC C1500 4.3. The PCM is from the 99 Vette. I'm running dual eFans.

I'm just not getting GND at A/C Clutch Relay Control (C2-43) which would energize the relay and engage the clutch.
PCM inputs:
A 51k resistor between 5v A/C Pressure Signal Ref (C1-45) and the A/C Press Sens Signal (C2-14) to bypass the 3 pin A/C Refrigerant Pressure sensor. I'm reading 2.5vdc.
From the OBS A/C controller, I'm applying 12vdc to A/C Request (C2-17).
The BIN says the type of AC is "3=Analog Cycling"
What am I missing??

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[L31MaxExpress]

Need help with the AC in my LS Swap. I installed a '99 Corvette LS1 into a 1996 GMC C1500 4.3. The PCM is from the 99 Vette. I'm running dual eFans.

I'm just not getting GND at A/C Clutch Relay Control (C2-43) which would energize the relay and engage the clutch.
PCM inputs:
A 51k resistor between 5v A/C Pressure Signal Ref (C1-45) and the A/C Press Sens Signal (C2-14) to bypass the 3 pin A/C Refrigerant Pressure sensor. I'm reading 2.5vdc.
From the OBS A/C controller, I'm applying 12vdc to A/C Request (C2-17).
The BIN says the type of AC is "3=Analog Cycling"
What am I missing??

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Disable the DTC for the refrigerant pressure sensor and wire like an 02 van. ECM needs a 12V ac request input and a ground on the cycling switch pin to operate in analog cycling mode.

 

[RDF1]

Something like this?

 

[L31MaxExpress]

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How my 97 Van is wired. Was basically the same with the Black Box, the 0411 and the P59. Had to disable the refrigerant pressure sensor DTC to make it operate. Saw the loss of pressure sensor signal with that DTC enabled as an empty system.
C2 55 needs a ground for the analog cycling setup to work. The stock cycling switch on the accumulator should be a ground signal on your 96 to start with. My 97 Express and 99 Tahoe both were.

 

[L31MaxExpress]

This is a typical black box AC diagram.

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[Kiko_Jones]

Huge thanks to everyone that provided information. The solution for me was to go into the PCM and change the "Type_Of_AC_On_Vehicle" to 2=Analog. The system work great now.
The '96 1500's A/C wiring has the Pressure Cycling Switch and A/C High Pressure Cutoff Switch in series which comprise the A/C Request Signal. If there's an issue with the system, that would be my safety.

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[L31MaxExpress]

Huge thanks to everyone that provided information. The solution for me was to go into the PCM and change the "Type_Of_AC_On_Vehicle" to 2=Analog. The system work great now.
The '96 1500's A/C wiring has the Pressure Cycling Switch and A/C High Pressure Cutoff Switch in series which comprise the A/C Request Signal. If there's an issue with the system, that would be my safety.

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Switches wired in series will work just fine. Must have wired the 96s a bit different. My 87 has the OE cycling switch feeding the clutch power and the high pressure switch on the back of the compressor is wired into the clutches ground circuit. I prefer ground side switching when I can.