I had my AC lines built with the attached 3 wire pressure sensor using the 3800 compressor however I haven't wired up the relay properly.
I tried to go back over my wiring instructions and discovered I had two different wiring setups and I some how I messed up both.

So here is how the car is wired right now and it doesn't work the compressor will not engage.

C203 pin d to clr 22
C203 pin n to ac relay 87

Compressor pin a to ground
Compressor pin b to ac relay 30
Clr 39 to ac relay 85
Ac relay 86 to ground

The three wire pressure sensor wiring instructions are the same with each set of instructions so no issue there.

This is the other set I have.

C203 Pin D to 22 PCM Clear AND TO 85 A/C Relay
C203 Pin N to 30 A/C Relay

39 Clear PCM to 86 A/C Relay
87 Relay To compressor clutch (+)
Compressor clutch (-) To ground

A A/C Pressure Transducer - Black - 80 PCM Blue
B A/C Pressure Transducer - Gray - Splice to Gray wire in 34 PCM Clear
C A/C Pressure Transducer - Red/Black- 27 PCM Clear

Which is correct? or are both wrong for my setup?
I'm setup using the PCM programed for a 2004 Chevy Impala, car is automatic.

The PCM grounds pin 39 Clear to activate the A/C compressor. So the top one where one side of the relay coil is wired to ground and then having the PCM ground the other side will never activate the relay.

I like the second set of instructions better (mine)

It doesn't matter which pin of the relay coil gets ground and which gets voltage just as long as one gets one and the other gets the other. Same with the relay contacts.

The only change you have to do from your existing wiring to make it work is change Relay 86 to run to C203 D instead of running it to ground (but also keep C203 D running to PCM Clear 22)

[This message has been edited by phonedawgz (edited 08-04-2014).]

Thank you, I made the one wire change and now the ac is working :-)
Thank you so much!

quote Originally posted by Fiero_Guy: Thank you, I made the one wire change and now the ac is working :-) Thank you so much!

When it comes to wiring Timm is the man. I am just preparing a swap that will use his 4.9L harness and its neat.
I wired my A/C system with the three wire sensor using the GTP compressor, a custom hose set and a new accumulator and its ice cold.
Just an off topic question, did you use the 2003 PCM or the 2007 with drive by wire? I took the easy way out , changed to cable operation of the N* TB and went with the 03 PCM. I like the series III engines and own two.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

I went back to cable throttle using a 2004 PCM out of a Monti Carlow SS.

quote Originally posted by Fiero_Guy: I went back to cable throttle using a 2004 PCM out of a Monti Carlow SS.

Almost forgot that the 3800SC series II engines were available in Impalas, Monte Carlo's, and Riveria' s until 2005. I believe that the PCM used was the same as on the 03 Grand Prix 3800's and is the only one supporting cable operation of the throttle body and support of the shifting of the 03-07 4T65eHD transmissions.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "