Need help with cooling system wiring (Dakota Digital Fan Controller & Vintage Air)

[dcdman67]

Hey guys,

I am getting ready to wire up my cooling system for my LS3 and cannot wrap my head around the wiring for this stuff. The components I am working with are:

2 Maradyne Fans on an AutoRad radiator
Dakota Digital PAC 2750 Fan Controller (http://www.dakotadigital.com/pdf/pac-2750.pdf)
Dakota Digital BIM 01-1 OBD II Controller (This will feed temp readings to the PAC 270)
2 Dakota Digital Relays per instructions
Vintage Air Gen IV System with Trinary switch

The instructions for the DD system are very straightforward. Where I am getting hung up is how it interfaces with the Trinary switch.

Any help would be appreciated. Im sure I left out a bunch of info that is needed so let me know if there are more details that I have missed.

Thanks in advance!

Dan

[sjaroslo]

This is my SECOND response because I realized that my FIRST response was complete and utter BS! Full of misconceptions and BAD information.

SO, I will say, I am just a NOVICE at this stuff myself, so take anything I say with a grain of salt! Or maybe the whole shaker, I don't know.

The instructions and wiring diagram for the trinary switch are here (http://www.vintageair.com/Instructions2013/904678.pdf)...

Also from the Vintage Air site, let's make sure we understand what the trinary switch does:
Binary Switch--disengages the compressor clutch with excessive refrigerant pressure or low threshold pressure (loss of refrigerant)
Trinary Switch--combines Binary functions with fan engagement signal

So, the purpose of the "compressor safety switch" (generic term for either binary or trinary switch) is to TURN OFF (or de-energize) the compressor when the system is over or under pressure. The difference between the two is that the binary switch just turns off the compressor but the trinary switch also theorizes that if our pressures are so messed up, chances are good that things in the AC system are overheated as well and additional cooling would be a good idea!

So, knowing that the trinary is a switch, we can see that the signal to energize the compressor passes through the trinary switch (on the black/green wire pair, coming from the "AC thermostat switch or compressor relay" and going to the compressor). So we know that when the trinary switch senses an over- or under-pressure situation, it will "open" the connection between the two black/green wires and stop the compressor from running--same thing that a binary switch would do.

The addition to the trinary switch is that it can turn the fan on, and this is obviously the circuit that the OP is more concerned with.

The way that it does that is by completing the circuit between the two Blue wires. This allows the current to flow from the "12V Key On Ignition Source" dark blue wire on pin 85 out pin 86 to one of the blue wires on the trinary, to ground. This small current flowing across the relay then allows the flow of the larger current that is coming from the Circuit Breaker red wire on pin 30 across the relay to pin 87 purple, which energizes the fan!

Now, in reality, the Electric Fan Relay that is depicted in the VA diagram isn't actually needed in the OPs arrangement, because all of those functions are controlled by the PAC-2750 itself.

SO, I would recommend that the "12V Key On Ignition Source" dark blue wire be connected to one side of the trinary switch blue wire, and the other side trinary switch blue wire be connected to the "A/C clutch cycle switch (+12V trigger)" wire on the DD. In this manner, when the trinary is calling for the fan, it will join the +12V signal from the harness on the car to the PAC-2750 A/C input wire, which is looking for just such a signal in order to energize the fan based on external input, rather than based on the actual temperature of the engine coolant.

[dcdman67]

Great explanation! That makes total sense. Should have the A/C charged and ready to go by the end of June so I will report back once I finish up the job.

[scottmccoy]

Very descriptive and technically useful information. I also wanted to know the method of wiring. This description helped me for the solution. Thank you for sharing.
air conditioning port st lucie (https://plus.google.com/103587002729772197042/about)

[sjaroslo]

Thanks for the kind words. File this under "occasionally even a blind squirrel finds a nut."

[MCB Matt]

GREAT write-up!!

Its actually very simple when its written that way right?

I'm sure you have helped a lot of guys on this. We get calls all the time about the Bi/Tri Switches... Which do i need? What does it do? Why do i need it? How is it wired?

I always suggest the Dakota PAC-2750 which i run in my builds too, its a great unit!

Matt

[mmosley]

So, the purpose of the "compressor safety switch" (generic term for either binary or trinary switch) is to TURN OFF (or de-energize) the compressor when the system is over or under pressure. The difference between the two is that the binary switch just turns off the compressor but the trinary switch also theorizes that if our pressures are so messed up, chances are good that things in the AC system are overheated as well and additional cooling would be a good idea!

Not exactly. Per Vintage Air the binary part turns off compressor if the pressure drops below 30psi or goes above 406psi. The third "leg" flips the fan switch on at pressures above 254psi. So, when your compressor is on and the high side pressure is high enough the fan comes on to help, it does not wait until you have an overpressure situation and it would not come on at low pressure. It is not a simple three way switch.