3 Fan Relay + VA - Diagram

[TA_C10]

Originally Posted by nsb29

If you are running three relays so that you will have high speed low speed you’re trinary switch only needs to trigger fan 2 which would turn both fans on high. ??

Yo, NSB29, I just read your post again, didn't see your question/suggestion under the pic the first time. Anyways.... At first I thought you may be right, but then I went over my diagram and if you follow the current flow and grounding I think if you only excite the high speed fan relay(ground), your going to get ground/power all the way through the circuit up to "relay 1 - 87". But because bosch style 5pin relays are "87a normally closed" you would need excitement through 85 and 86 to flip the switch from 87a to 87 which would then open up the current from pin 30 to 87. So your only going to get the high side fan to run by itself full speed.

Am I thinking correctly here guys? I'm not at a point where I am ready to hook a battery up yet, but very close, so I will test this theory very soon unless ya'll can confirm my thought.

[nsb29]

I have not tried to dissect your drowning but this is how I have have understood the way it works with 3 relays
Low speed turns on relay 1 contact 87 and runs through relay 3 contact 30 in series so that both fans run on 6V When fan 2 is turned on relay 2 switches relay 3 from 87a to 87 witch then grounds both fans and turns off 87a on relay 2 now both fans receive 12V for high speed

[TA_C10]

Originally Posted by nsb29

I have not tried to dissect your drowning but this is how I have have understood the way it works with 3 relays Attachment 1979084
When fan one comes on they are wired in series so that both fans run on 6V When fan 2 is turned on relays 1/2/3 switches switch from 87a to 87 witch then grounds bought fans and turns off 87a on all three relays now both fans receive 12V for high speed

Yeah but low speed always starts first right? And then it "stays" grounded/triggered when the high speed ground trigger fires giving you full voltage.

So if for some reason your low speed fans are not triggered by the ECM because engine temps are not high enough, and A/C pressure rises too high for some reason, it's only going to ground/trigger the high speed fan which only grounds relay 2-3.

If this is incorrect let me know.

[nsb29]

Originally Posted by TA_C10

Yeah but low speed always starts first right? And then it "stays" grounded/triggered when the high speed ground trigger fires giving you full voltage.

So if for some reason your low speed fans are not triggered by the ECM because engine temps are not high enough, and A/C pressure rises too high for some reason, it's only going to ground/trigger the high speed fan which only grounds relay 2-3.

If this is incorrect let me know.

I went back and studied what you’re saying I was thinking fan 2 turns both fans on high but you’re right it only turns fan 2 on high if fan 1 is off so if you’re motor is cold and you turn the a/c on your only going to have fan 2 on high

[SunSoaked]

You could just install the Dakota Digital controller, hook up a few wires, program your setpoints and be done with it.

[nsb29]

Nothing from Dakota digital is cheap A three relay set up works just fine and you still have a few wires to hook up The Temp’s are programmed into the ECM I am using the windstar fans. Fan 1 is wired to low speed, and fan 2 is wired to high. Previously I said the trinary turned on high speed fans, but I was confused it only turns on high speed fan when low speed is off. I have my trinary wired to fan 1 and both fans come on, then when fan 2 comes on both fans run on high. Electrical is not my expertise and explaining it is harder lmao