Any C4 c68 A/C system experts?
Thread Starter
Burning Brakes
Joined: Sep 2008
Posts: 810
Likes: 58
From: Alva Florida
Any C4 c68 A/C system experts?
This has been bugging me for a while now.....
1990 Corvette, C68 a/c with a 421 stroker, 950 HP Holley (I know, I know) healthy cam, headers, ect. It actually runs great.
I currently have the a/c hooked up to a toggle switch on my dash grounding the a/c relay and all the C68 a/c controls work (fan speed, defrost, and the rest). I am considering putting a FIRST EFI Intake and FAST Stand alone EFI harness on it.
When I questioned Ken at FIRST (a really good guy) about the a/c activation he said that he thought that the a/c on TPI cars only grounded a relay when switched on, and only changed the stepper motor on the iac.
If this is true, my a/c should be turning on when I use my c68 a/c panel (even with a carb). If I go with the FAST EFI, can my a/c work, or do I still need the grounding switch?
I'm also changing to smaller heads, and a smaller cam to be more streetable and closer to original appearance and operation . I've had my C4 for 18 years and it's time for a change.
Any help is greatly appreciated.
1990 Corvette, C68 a/c with a 421 stroker, 950 HP Holley (I know, I know) healthy cam, headers, ect. It actually runs great.
I currently have the a/c hooked up to a toggle switch on my dash grounding the a/c relay and all the C68 a/c controls work (fan speed, defrost, and the rest). I am considering putting a FIRST EFI Intake and FAST Stand alone EFI harness on it.
When I questioned Ken at FIRST (a really good guy) about the a/c activation he said that he thought that the a/c on TPI cars only grounded a relay when switched on, and only changed the stepper motor on the iac.
If this is true, my a/c should be turning on when I use my c68 a/c panel (even with a carb). If I go with the FAST EFI, can my a/c work, or do I still need the grounding switch?
I'm also changing to smaller heads, and a smaller cam to be more streetable and closer to original appearance and operation . I've had my C4 for 18 years and it's time for a change.
Any help is greatly appreciated.
Drifting
Joined: Jun 2020
Posts: 1,710
Likes: 739
From: Stay dangerous my friends
I have an older C68 car where the ECM does not try to turn the AC off... but look at the wiring schematic in the FSM for the AC system, the ECM function could easily be bypassed, it doesn't do anything funny with the computerized controller. Ultimately there's a solenoid which activates the AC compressor clutch, the C68 controller, the low pressure switch, blower control module on some cars and ECM n others, and the high pressure switch, determines that it's "on" and any of those systems also can be easily bypassed (can be for testing, not should be).
Racer
Joined: Sep 2001
Posts: 365
Likes: 93
From: Chesterfield VA
This has been bugging me for a while now.....
1990 Corvette, C68 a/c with a 421 stroker, 950 HP Holley (I know, I know) healthy cam, headers, ect. It actually runs great.
I currently have the a/c hooked up to a toggle switch on my dash grounding the a/c relay and all the C68 a/c controls work (fan speed, defrost, and the rest). I am considering putting a FIRST EFI Intake and FAST Stand alone EFI harness on it.
When I questioned Ken at FIRST (a really good guy) about the a/c activation he said that he thought that the a/c on TPI cars only grounded a relay when switched on, and only changed the stepper motor on the iac.
If this is true, my a/c should be turning on when I use my c68 a/c panel (even with a carb). If I go with the FAST EFI, can my a/c work, or do I still need the grounding switch?
I'm also changing to smaller heads, and a smaller cam to be more streetable and closer to original appearance and operation . I've had my C4 for 18 years and it's time for a change.
Any help is greatly appreciated.
1990 Corvette, C68 a/c with a 421 stroker, 950 HP Holley (I know, I know) healthy cam, headers, ect. It actually runs great.
I currently have the a/c hooked up to a toggle switch on my dash grounding the a/c relay and all the C68 a/c controls work (fan speed, defrost, and the rest). I am considering putting a FIRST EFI Intake and FAST Stand alone EFI harness on it.
When I questioned Ken at FIRST (a really good guy) about the a/c activation he said that he thought that the a/c on TPI cars only grounded a relay when switched on, and only changed the stepper motor on the iac.
If this is true, my a/c should be turning on when I use my c68 a/c panel (even with a carb). If I go with the FAST EFI, can my a/c work, or do I still need the grounding switch?
I'm also changing to smaller heads, and a smaller cam to be more streetable and closer to original appearance and operation . I've had my C4 for 18 years and it's time for a change.
Any help is greatly appreciated.
