ECU Controlled Fans - VA Binary or Trinary Switch
 

I am working through the wiring on my car and wanted to know if anyone had a wiring diagram for relays that are using the E38 ECU to control their fans with a vintage air trinary switch.

From what I have read you have to introduce a 3rd relay for the trinary trigger or the ECU will see it as a fault.

Appreciate the help!

my gmpp unit has a ac trigger wire once i installed the pcm of nc fan bump and electric fan kit. after installing that i used a binary switch.

I don't have a diagram, but have recently ordered a complete VA system. It is still all in the boxes. The rep did tell me a trinary switch was required for proper operation for an LS swapped car.

There's this generic video:

https://www.youtube.com/watch?v=l604JCZx_ow

And this link I had saved:

http://ls1tech.com/forums/conversion...-question.html

Not sure if any of these will help, because I'm not at this point yet myself. Let us know how it goes.

I have actually read through those same links and nobody offers a solution for the fact the ECU will read the negative trigger from the trinay switch as a fault.

Plenty of people say they add a 3rd relay but I cant seem to locate a wiring diagram for this scenario. I know how to get the fans to work using the negative (hi/low) trigger from the ECU but I can't figure out how to add the trinary switch into the mix....

I gave up trying to get the E38 to control twin fans. I used the entropy fan controller. It has has an AC trigger wire, and the dip switches let you easily set the on/off temps for each fan. I know this isnt exactly the answer to what you are asking, but its an option. Scott

I found this on a C10 truck forum. It appears that it will work but I am open to comments on this. Worst case is that the fans are powered by more than one relay under some circumstances but I don't think that should be a problem...

I have seen the entropy controller and its a nice setup.

http://i.imgur.com/XIpUdtF.jpg

That will work fine. I did the same thing several years ago. I prefer the series/parallel low/high setup, but this will work, just a little noisier in low speed.

Don

I talked to a buddy of mine today (from camaros.net) that has that same setup and likes it a lot. If you have the GMPP harness, it seems like a nice way to go.

It was very simple and works like a charm. Cut a wire, add a wire, Run a wire or two, new relays and fuses in the fuse box and your done. Just like OEM.

Yeah I just bought the fan and bump kit last night. They have 10% off until tonight.