Trinary and 3 relay electric fan questions

[SilverGT3RS]

Hey everyone-

I’ve been searching around trying to find an answer for adding AC to my LS swap-lots of info floating around, but also a lot of conflicting info. To add to the confusion theres a lot of info that’s 10 years old.

First an overview of my setup. 2004 6.0 LQ9 out of a Cadillac Escalade. Using factory PCM and main wire harness, DBW. I have HP Tuners. Engine and trans swapped over into a 67 C10, using aftermarket radiator with 2 electric fans with 3 relay harness -using green and blue wire to drive fans via the ECU similar to the schematic below.







I’m adding a Classic Air system, and from what I’ve read using the trinary switch is the simplistic way to go.

My confusion comes from some guys saying you need a diode wired inline if you hook the blue trinary wire to the fan relay to keep from throwing the check engine light.


Others show using a small separate relay. Problem there is I couldn’t find any info on relay size. I’m assuming it would need to be 30-40 amps? I’m also assuming I’d need a busbar of some kind?



What’s the easiest way to accomplish turning on the fans when using the AC with my setup?
Should I be exploring anything outside of the trinary switch?

Thanks in advance!

[Accelo]

You question is clear as are the schematics. Must have taken you some time to post this. Great job BTW.

The Trinary Switch only grounds the relay so it can start one fan. This isn't really needed at all. You could use the Trinary switch to ground the Fan trigger #2 and it will bring in the high speed relay. I recommend running both fans when the Air is running. It will help keep the refrigerant pressures lower. I hid the relays behind the battery between the battery and the core support. This was a pain to make all the relay connections and still have it look appropriate.

I am using the same three relay set up for my fans. Works great with both fans running half speed till the other relay closed then it's full speed/voltage for both fans.

Diode are used to control the back EMF produced when the relay coil collapses. I didn't install any. I haven't had any issues so far but I really haven't driven in heat.

Cheers

[SilverGT3RS]

Originally Posted by Accelo

You question is clear as are the schematics. Must have taken you some time to post this. Great job BTW.

The Trinary Switch only grounds the relay so it can start one fan. This isn't really needed at all. You could use the Trinary switch to ground the Fan trigger #2 and it will bring in the high speed relay. I recommend running both fans when the Air is running. It will help keep the refrigerant pressures lower.

I am using the same three relay set up for my fans. Works great with both fans running half speed till the other relay closed then it's full speed/voltage for both fans.
Cheers

Thank you for replying! So basically I’m going to bring my wire off the trinary switch to the blue trigger wire off the PCM correct? This diagram shows it on the green wire for low speed fans, but it’s the same concept?





Did you have to wire in a diode on the PCM side to keep from throwing a CEL? Seems to be hit or miss from all my research. I was going to start without a diode and see what happens.

[ls1nova71]

The resistor is generally to keep the PCM from seeing a ground on the fan control circuit that it didn't send. If it sees that ground, it assumes there is a short in that circuit, and therefore will trigger the CEL. Since you have HPTuners, I would just forgo the resistor and just turn off the error reporting on that circuit.

Also, if you hook the trinary to that green wire, you will get both fans on low when the AC needs it, but if you hook it to the blue wire you will only get one fan on high, but if the engine temp is already high enough to have them on, and let's face it, whenever the air is on, it's hot enough, you will get them to both come on high. So I would personally hook it to the blue wire.

[SilverGT3RS]

Originally Posted by ls1nova71

The resistor is generally to keep the PCM from seeing a ground on the fan control circuit that it didn't send. If it sees that ground, it assumes there is a short in that circuit, and therefore will trigger the CEL. Since you have HPTuners, I would just forgo the resistor and just turn off the error reporting on that circuit.

Also, if you hook the trinary to that green wire, you will get both fans on low when the AC needs it, but if you hook it to the blue wire you will only get one fan on high, but if the engine temp is already high enough to have them on, and let's face it, whenever the air is on, it's hot enough, you will get them to both come on high. So I would personally hook it to the blue wire.

Good stuff. First off I appreciate you guys trying to help me out.
On my swap, I had a custom built 3 relay harness made to go with my radiator and electric fan conversion. After reading the replies I went out to the shop and saw the harness guy made it easy for me…there is a small harness that has the green and blue PCM trigger wires that run with the main relay harness.



The 2 wires at the top of picture run to the PCM, bottom 3 wires towards relays for reference.
I’m thinking I can pull apart the Weather pack connector and bring the trinary wire into the end with the 2 blue wires, combine the 3 blue wires, recrimp and plug back in.

Does that look like it will work?

[kglowacky]

doing the same install. Is there a specific type of Trinary switch I need as far as voltage. high and low pressure and refring. type or are they all the same as long as they screw into the factory dryer? Thanks

[SilverGT3RS]

Originally Posted by kglowacky

doing the same install. Is there a specific type of Trinary switch I need as far as voltage. high and low pressure and refring. type or are they all the same as long as they screw into the factory dryer? Thanks

Correct. All the trinary switches I’ve seen have 4 wires and work off the high/low pressure of the AC system. I didn’t trust Amazon so I paid a bit more and got it direct from Vintage Air.

[Richard]

Oem and aftermarket PWM controllers only bring the fan/fans up 40-50% with a cooling call. Of course highest call for cooling takes preference. So if engine wants more cooling, fan will speed up. See no reason to run fans on high with a cooling call only. Am using PWM myself. If I was using a two speed setup my fans would come on at low with cooling.

[ls1nova71]

There's no reason to run the fans on high when it's just cooling the engine, but with AC, you almost can never have too much cooling capacity.

[dec010974]

Hello to all. I hope I’m not imposing on this thread. I am using the champion radiator, dual fan combo for my lsx swap. Is there any reason to use the 3 relay setup? I don’t know if my fans have 2 speeds. Also I hope to add ac soon. It’s hot in Miami Florida.

[Accelo]

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[Accelo]

The set up that came with my radiator had a system that ran one fan at full speed at the lower cut in from the ECM and started the other fan at the high temperature cut in from the ECM/ECU. (The first fan continues to run with the second fan on). It was my preference to have the quieter low speed on both fan option. It is way more complicated and in general I would not recommend it because of the wiring complications it introduces.

My fans were not advertised as two speed. Just running them in series cuts the voltage and thus the speed of both fans. It also requires another relay (three instead of two).
I would rate this as not typically worth the hassles as the motor will stay just a cool either way.