Vintage Air Trinary switch wiring, PSI harness

[class67]

I'm sure this has been covered 1000 times already, but I am trying to figure out how to wire the trinary switch for my VA system. I have a PSI harness with 2 wires for the fans, but how do I incorporate the trinary switch to turn on one of the fans without interrupting the ECM? this is an LS3 swap, Griffin Radiator, twin fans with PSI harness.

Thanks for any help that you can provide...did I mention that I hate wiring! https://static1.pt-content.com/images/pt/2018/01/shakehead-1.gif

[KUL FIR CHICK N]

I'm not familiar with the PSI harness, but brushed fans are typically operated by relays. The relays are typically switched on the ground side. Most ECMs also use "active low" outputs for fans which means they ground the outputs when fans are required, activating ground side switched relays and turning on the fans. If you are wired in this way, you'll simply ground one side of the VA trinary switch (blue) and hook the other side (also blue) up in parallel with the ECM output. This way, either the ECM or the trinary can trigger the fan relay. They won't interfere with each other.

Ryan










I'm sure this has been covered 1000 times already, but I am trying to figure out how to wire the trinary switch for my VA system. I have a PSI harness with 2 wires for the fans, but how do I incorporate the trinary switch to turn on one of the fans without interrupting the ECM? this is an LS3 swap, Griffin Radiator, twin fans with PSI harness.

Thanks for any help that you can provide...did I mention that I hate wiring! https://static1.pt-content.com/images/pt/2018/01/shakehead-1.gif

[KUL FIR CHICK N]

Sorry guys, I just realized I had an error on the wire color for the trinary switch. I have already corrected it above. The blue wires on a VA trinary switch are the fan trigger circuit and the black/green wires are the AC pressure safety switch circuit. Sorry for the confusion.

Ryan

[badazz81z28]

Correct, you have the trinary operate a relay via ground activation. I have two fans, one is controlled by the ecm and the other is wired to the trinary switch and a thermal switch on the radiator.

[dhutton]

Correct, you have the trinary operate a relay via ground activation. I have two fans, one is controlled by the ecm and the other is wired to the trinary switch and a thermal switch on the radiator.

You never give it up, do you? Seriously it can also be used to switch a 12 volt signal just as easily as a ground depending on the design that someone is implementing...

SMH,
Don

[KUL FIR CHICK N]

You never give it up, do you? Seriously it can also be used to switch a 12 volt signal just as easily as a ground depending on the design that someone is implementing...

SMH,
Don

Agreed. It's just a switch. You can use it how you wish, as long as the rest of the fan harness is set up properly. We have seen plenty of folks with the fans wired-up improperly to the AC system that cause the compressor to engage when it's not supposed to. This typically happens when people don't have a trinary switch and are triggering the fans off the compressor clutch power lead.

Ryan

[dhutton]

Agreed. It's just a switch. You can use it how you wish, as long as the rest of the fan harness is set up properly. We have seen plenty of folks with the fans wired-up improperly to the AC system that cause the compressor to engage when it's not supposed to. This typically happens when people don't have a trinary switch and are triggering the fans off the compressor clutch power lead.

Ryan

Thanks for weighing in. Hopefully it will reduce some of the confusion leading to these wiring errors. Maybe VA should incorporate some kind of fan control option or module in your systems...

Don

[class67]

Ok, so what I have done is wired up another SPAL FRH relay as follows:
Red - to fan
Orange - 12v switched
Yellow - 12v bat
grey - wired to the compressor

Will this work? and do I absolutely need to wire up temp sender as well? if so, just tie into the grey wire, correct?

[dhutton]

Not following this. Where is the trinary switch?

Don

[KUL FIR CHICK N]

Grey goes to one of the blue wires on the trinary and the other blue goes to chassis ground. This will ground the grey wire when AC head pressure reaches 254psi, closing the relay contacts and turning on the fan. You don’t have to wire in the temp switch, but I would. Just tie it in with the grey. The switch grounds when it reaches its set point.

Ryan

[class67]

That's what I thought, thank you for the confirmation!

[MAGONSTERZ68]

Grey goes to one of the blue wires on the trinary and the other blue goes to chassis ground. This will ground the grey wire when AC head pressure reaches 254psi, closing the relay contacts and turning on the fan. You don’t have to wire in the temp switch, but I would. Just tie it in with the grey. The switch grounds when it reaches its set point.

Ryan

this is the set up i used as well with V/A and psi harness, all worked well unit the elec servo heater valved started the tick of death, V/A was tech was quick to ship one out to me as it has been an issue in the past. unfortunately for me it went out at the exact time my trinary switch took a dump and would not engage my a/c pump clutch and in my frustration ordered it before calling to see if V/A would warranty it. oh well it 102* around here these days and would rather have my part sooner than later. Has anyone else ever had a trinary switch go bad?

[dontlifttoshift]

I have seen one in the past 20 years.......a wire broke off where it is soldered on to the switch under the rubber cap. That's the only one I have had fail.

[MAGONSTERZ68]

peeled back the rubber cap and no solder detaching issues just would not see pressure to close connection to engage the compressor, swapped out trinary today, will have to get a vac draw on it and fill with to factory recommended specs. while system was down moved the condenser closer to the radiator, 1" from almost 1.75" in hopes to bump air flow across it.