Very confused on AC wiring...

[Power Surge]

Let me preface this by saying I've spent a good amount of time looking into GTM AC wiring. I've accumulated about 6 or 7 different GTM AC wiring diagrams... and all of them are different.

My combo is the stock 97 Vette ECM, with the GTM Vintage air, and I will be doing the solenoid/mechanical heater valve.

I see the Vintage Air can have it's own dedicated wiring. It's diagram shows a binary switch. But it seems everyone is using a Trinary switch.

Other diagrams use either stock or aftermarket ECU control mixed with the Vintage Air. But there's no detailed wiring shown coming from the ECUs (i.e. conntector PIN numbers).

I would imaging the downside to the VA only setup, is no WOT shut off or programmable pressure control.

I can see the upside of using OEM ECU control, but I am not sure how you'd wire in the VA controls to request the AC circuit of the stock ECU.

So what it the preferred method for my combo? And how does it get wired?

[Power Surge]

Ok....so I was searching on the other site, and I actually found a post by the previous owner of my GTM about this. He posted the following diagram that he made...




Does this all look good?

[VRaptor SpeedWorks, LLC]

I would definitely try to use the engine ECU to control the AC compressor if possible. It makes everything a ton easier. You get control of the AC compressor for WOT and so the compressor kicks out above redline....which I think the normal "redline" for the compressor in the ECU is programmed to something around 4600 RPM? You also get idle speed control...which is probably the #1 reason....so that when you have the AC on, your engine doesn't stall at idle. You also get cooling fan control (assuming that you have the cooling fans wired to the ECU) so that the fans kick on and off as needed with AC pressure.

Yes, that diagram pretty well covers it.....but you're going to have to make sure that the pin numbers are correct for the 97 ECU that you have. The ECU pin numbers and wire colors are different for different years.....I think 97 and 98 are the same....and 99-04 are the same?.....but I would look up the actual ECU wiring for your model year to be sure. Also, in that diagram you posted, it's the blue wire out of the VA relay that you want to connect to the "AC request" pin of the ECU.....the diagram you posted makes it look like it's dark green.....which is the wire color in the C150 connector. Again....I would make sure that you have the right schematic for the C150 connector as I think those wires changed also depending on the year of the ECU/donor vehicle. You use the donor pressure sensor in this installation, which gets installed in the AC hose right in front of the crank pulley in the tunnel.

On the heater control valve, if you're going to install one, make sure that you plumb in a way for the coolant to bypass the valve so you always have circulation between the 3/4" and 5/8" heater hoses out of the waterpump or you'll have overheating issues.

[Power Surge]

Thanks Shane. On the heater control valve I was going to do crashes set up which I believe takes care of that issue, correct? I actually have both of those parts that came with the car but because of the age I will buy new fresh ones.

[VRaptor SpeedWorks, LLC]

Yes, Crash's set up solves the coolant circulation issue.