64-66 C10 vintage air with LS question

[Justin71105]

Anyone have LS swap with vintage air, need help with fan relay to trinary switch.

So I have a 64 C10 and have most of the Vintage Air system installed. Having an issue understanding the trinary switch wire going to fan relay. I have put almost 1000 miles on the truck without heat/ac. Fan works like it should, I wired the fan relay using my PSI harness diagram.

Pin 85 - PSI wire that sends signal for fan....think this is out to trinary
Pin 86 - Switched power
Pin 87 - Constant power
Pin 30 - Power out to fan


Vintage airs diagram shows

Pin 85 - Switched power
Pin 86 - Out to trinary and engine temp sensor (optional)
Pin 87 - Power out to fan
Pin 30 - Constant Power


The other connections I understand from there diagram for that switch.

Have everything installed except for rubber pressure lines and finishing up some wiring. Cracked my trans cooler fitting and waiting on a replacement. Should have the heater working by next weekend and maybe ac by the next.

[A1971Blazer]

My '67 has two fans, I wired the PCM fan 1 wire, which simply grounds the relay, and the ground from the trinary switch together to the relay ground (85) for fan 1
85 and 86 can interchange since they only energize the coil that closes the main contacts,
so either the pcm or the trinary switch, (or both depending on engine tempº) will provide the ground when the fan is needed.

[Justin71105]

Ok so trinary switch blue wire to pin 85. Which will ground ac when running or if bot running temp switch will turn on fans.

[A1971Blazer]

Originally Posted by Justin71105

Ok so trinary switch blue wire to pin 85. Which will ground ac when running or if bot running temp switch will turn on fans.

Yes, that's how mine is wired and it works perfectly.
If the AC is off, the fan will come on at the programmed engine tempº via the PCM
If the AC is on, the fan will come on as determined by the trinary switch or by the engine temp or both combined.
Once the fan starts by engine temp, the trinary ground is just redundant since the fan is running already.

[Justin71105]

All right I appreciate the help. I was thinking the PCM ground was sending a signal to the trinary or something like that. I didn't think about the fan needing to run to cool the condenser when the AC was on.

I'm going to switch the constant power and out to fan to get the power on the switch relsy instead of the other side. I don't think it matters but I think that's standard wiring.

[A1971Blazer]

Originally Posted by Justin71105

All right I appreciate the help. I was thinking the PCM ground was sending a signal to the trinary or something like that. I didn't think about the fan needing to run to cool the condenser when the AC was on.

the trianry switch is designed to protect the AC circuit from over (or under) pressure in the refrigerant system.
The first thing it does is turn the fan on to cool the condensor and drop the pressure, if that doesn't happen, it will shut off the compressor when the pressure reaches the limit.
(you may already know all this)

87(or 87A) to 30 should be the main power circuit for the fan
87 can be constant or switched either one....mine is wired for constant 12V
again 85 and 86 are the trigger connections, and don't need a specific polarity to work.

[A1971Blazer]

I built a custom load center for my swap to centralize the under hood electrical system

[Justin71105]

Did not know that, thanks for the explanation. There wasn't a wiring schamtic for the switch internals only a diagram to wire it up. Was trying to think of ehat the switch actually did going off the small window in diagram that tells the different pressures it switvhes at.

I thought the ground from pcm was sending a signal to trinary letting it know fan was running. Didnt think about the trinary telling the fan to come on.

Still have to connect all the wiring other than battery connections and what plugs into the under dash unit.

Hopefully I will have it fully installed over the next two weekends. Waiting on a new trans cooler and then its just wiring and cut/crimp compressor lines.

Then hope for a warner day to charge the refrigerant, or borrow a propane heater from someone to warm garage while I do it.

[Justin71105]

Originally Posted by A1971Blazer

I built a custom load center for my swap to centralize the under hood electrical system
Attachment 2326632

That box under the hood in my picture is my relay box with fuses then that other little box beside it is my switched fused power I'm likely going to move this to that larger black box as well.

I would have put the vintage air relay in there as well but their harness does not reach that far so that really is going to be behind the glove box.

[A1971Blazer]

Originally Posted by Justin71105

That box under the hood in my picture is my relay box with fuses then that other little box beside it is my switched fused power I'm likely going to move this to that larger black box as well.

I would have put the vintage air relay in there as well but their harness does not reach that far so that really is going to be behind the glove box.

nice work....
Once the VA unit and all the hoses go in behind the dash, it gets tight under there for sure. I mounted the relay to the bracket that holds the evaporator unit.
There isn't a wiring harness on mine that hasn't been stripped and re-worked. In the end it's all worth it...

My box looks neat from the top...from the bottom it's like a spider web
I made a couple of copper buss bars for the hot and ground to eliminate a lot of extra wires coming into it.
I added a couple of relays for the headlights so I can get full voltage to them
I used the factory wires from the dimmer switch as the trigger wires.

[Justin71105]

I'm going through my wiring one day to clean it up and also replace some wires.

I ran out of black wire and used red on the 2 post terminal in the picture. That post goes to frame ground, but I ran out of the correct size black wire and used red.

I also used butt connectors in a few spots and will be replacing those with the solder type water seal connectors.

So far it has been good with no issues, drives very well. But I dont want the electrical issues down the road from using standard butt connectors.

Once I get ac/heat going I will go start slowly going through and taking care of the wiring

Should have done it correctly from the start but I had never undertaken anything like this.

[A1971Blazer]

Originally Posted by Justin71105

I'm going through my wiring one day to clean it up and also replace some wires.

I ran out of black wire and used red on the 2 post terminal in the picture. That post goes to frame ground, but I ran out of the correct size black wire and used red.

I also used butt connectors in a few spots and will be replacing those with the solder type water seal connectors.

So far it has been good with no issues, drives very well. But I dont want the electrical issues down the road from using standard butt connectors.

Once I get ac/heat going I will go start slowly going through and taking care of the wiring

Should have done it correctly from the start but I had never undertaken anything like this.

wiring is a PITA but it's better to take your time and make sure it's correct to prevent a major disaster...
I used butt connectors only on the power window connections to the motors.
Even there I used the adhesive type heat shrink tubing over them to seal them against corrosion.
I bought several of the Packard 56 connectors that were originally used on these trucks for nearly all the connections inside.
Under the hood, I used the weather pack connectors

[Justin71105]

It is definitely a pain, going to get a 02 suburban upper radiator hose this weekend from pick-n-pull.

The one I got originally fit but cut it about 1" too short and I think it was the suburban one. Been a few years and the writing is wore off so can tell.

Replaced it with the gates 21439 and it isn't molded right to fit even trimming.

Found a picture of someone using the suburban one cut down and it fits well. If I get it right I'll buy a new one and cut it the same.

Running a champion 4 core, passenger side in/out sized for ls water pump. Have the 5.3L stock truck water pump. Lower hose fits really well, cant remember what it came off of.