Robs69

Hey Guys, fairly new here. I have looked at some of the threads and can't seem to find what I'm looking for. Maybe I can get some advice or tips on what issues I am having.

To start off I had my truck wired by a friend. At the time when i got the truck back, everything seemed functional, the 1st fan would come on with temp, and the second fan would come on when I turned on my A/c controller (even though it wasn't charged at the time). Long story short I get my A/C charged and i can turn on the a/c it blows cold as could be, but when I turn it on I could be idling with the voltmeter on my dakota digital gauges holding at 14v and when i turn it on it will drop to about 10v and recover. Now initially i didnt think this was an issue until i notice that it does it everytime the compressor cycles on and off. It started to bug me the more I thought about it. So I don't know enough truthfully about A/c systems but figured you guys could maybe point me in the right direction.

It is a ls1 out of a GTO installed in a 69 chevy truck. To give you a run down of the stuff i have on the truck, The engine harness I am running is made by PSI with a Pcm programmed by them. I am running vintage air with a binary switch with two entropy electric fans. I am running two 1000w amps. Originally I had a 140amp Alt and thinking that my alt might be not necessarily the issue but unpowered I bought a high output alt made by singer alts, 370amps. The psi harness came with a 8ga wire from the alt to the starter, so I upgraded all of my grounds and power leads to 1/0. (probably overkill).

I started out looking at the wiring diagrams for the vintage air verifying that the power and ground to the vintage air unit were to the battery as specified. The ground that was being used went to the firewall but i don't think that there was a great/clean ground from the cab to the frame or engine so i unhooked the battery leads & ran a 10 gauge ground from vintage air to the engine, with the frame to engine connection. Right now i can Let the truck run up to temp for 20 minutes and no fans turn on until i turn on the ac. Now i checked for the 12v on the ac signal and it appears to be getting the 12v, (i don't notice an increase in the rpms). I did ring out all of the wires and drew out all of the relays which ill post below. Can this work with a binary switch? Is that my issue? hopefully someone of you can shed some light on this and point me in the right direction. Thank you.

garys 68

iTrader: (1)

Run a fan on a trinary switch. VA warns against running anything else off the AC request.

Robs69

So I would technically have to pull the binary and have my system recovered to swap It right

garys 68

iTrader: (1)

I believe there's a shrader valve under the switch, check with VA.

ryeguy2006a

iTrader: (27)

In your tune do you have the A/C compressor as Fixed like a truck or variable like the LS1 engine? That may be causing some of the issues if the compressor is expecting to cycle, but the stock settings from the LS1 ECU are looking for pressure settings.

garys 68

iTrader: (1)

I have a stock truck tune but with no connection between AC and computer.
I used the stock truck low and hi (recirc) fans. The high is triggered by the ecu and/or the trinary switch relay grounding. Others have done this and got a fan code due to the trinary, but I did not on mine.

Robs69

Truthfully I don't know. It's whatever psi programmed it to. I remember telling them what i was doing with it. Do the circuits look ok to you guys or why do you think im getting the huge voltage drop? Would the type of compressor matter? The power feeding the fan relays i believe is fed from the dash harness, could there be too much current for that? Or you think in should have it looked at? I do need to have it tuned still.