3 Fan Relay + VA - Diagram

[TA_C10]

What do you guys think? This is how I am planning to wire a trinary switch off my Vintage Air to my 3 relay fan setup.

MDPotter thanks for helping me put this together

[First c10]

So the grounded trinary “Blu” has a diode to the high and low side of the pcm so the fans go to high when the trinary switch see’s pressure? And if the pcm tries to turn on the fans it doesn’t change? Will there be any codes in the pcm as the high and low signal wire will see ground when ac is on and the pcm isn’t calling for fans on? I Ask because I can’t remember what I did.

[TA_C10]

Originally Posted by First c10

So the grounded trinary “Blu” has a diode to the high and low side of the pcm so the fans go to high when the trinary switch see’s pressure? And if the pcm tries to turn on the fans it doesn’t change? Will there be any codes in the pcm as the high and low signal wire will see ground when ac is on and the pcm isn’t calling for fans on? I Ask because I can’t remember what I did.

The trinary has 2 blue wires and 2 black wires. One blue goes to trigger relays when it see pressure, the other blue wire is grounded on trinary. One black goes to compressor clutch, other black goes to switch/thermostat. So yep, I have it turning on full power so both fans high speed.

If PCM turns on fans those diodes are one way only so it won't back feed into trinary. No change. And it's my understanding the resistors plus diodes keep the PCM from seeing ground and stop codes from being thrown. MDPotter showed me this part so I'm hoping we're correct on this.

FirstC10, does your setup throw codes?

[First c10]

I have mine setup to kick the high side wire (which will only run 1 fan) so if the motor get above 195 the pcm will initiate the low speed and I will have high speed both fans. I think this is how mine is wired. I never thought about the diodes. I may change mine. No codes so far but haven’t ran it much with the ac on.

[TA_C10]

I wonder if the A/C is running that I would ever need the low speed trigger from trinary. Chances are the engine already running hot enough low speed is triggered.

PS:. MDPotter has a better diagram. I just modified it on paper to reflect my setup. I didn't think it was my place to post it so maybe he will see this post and put the good stuff on here

[MDPotter]

Here it is! I attached it as a PDF so it's easier to download.

Dual Fan GM Schematic w trinary switch incorp.pdf

[ls1nova71]

Originally Posted by TA_C10

I wonder if the A/C is running that I would ever need the low speed trigger from trinary. Chances are the engine already running hot enough low speed is triggered.

You most likely never would, since in the summer when the AC is generally used, the engine will already be warm enough that the low fan will already be on, with the exception of when you first start it. I've wired several swaps with only the high triggered by the trinary switch and it has worked fine for well over 100k miles on them. That said, it wouldn't hurt to wire both of them up, but just not really a necessity.

[nsb29]

Originally Posted by TA_C10

What do you guys think? This is how I am planning to wire a trinary switch off my Vintage Air to my 3 relay fan setup.

MDPotter thanks for helping me put this together

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. ??

[MDPotter]

This is going to be long-winded.

It is not necessary to wire the trinary into both fans, but I prefer it that way. As Ls1nova71 said, it is rare that there will be a situation where the PCM will not be calling for either fan to come on but the AC pressure will be high and trigger the fan(s), but the OCD in me says to hook up both fans to the switch to guarantee that both fans will run on high when the pressure setpoint is reached. That way, you have both fans pulling across the entire radiator/condenser to lower that pressure. In my mind, that will reduce the risk of damaging any AC components.

Here's how my Gen 3 LS works:
-Coolant temp reaches around 190 and the PCM grounds out the low speed control wire (green wire, connector C1 pin 42). This wire remains grounded until coolant temp is below 190. Both fans on half speed.
-Coolant temp reaches around 205 and the PCM grounds out high speed control wire (dark blue wire, connector C2 pin 33). This wire remains grounded until coolant temp is below 205. Both fans full speed.

I found this out while wiring because I was curious. I was able to confirm that both wires have to be grounded in order to have both fans running full speed. If only the high speed control wire is grounded, fan 2 will run full speed and fan 1 will be off. Not a likely scenario, but it's only one more wire to hookup.

[TA_C10]

Good info here. Potter I'm going to go ahead and wire both like we talked about. I have the diodes and resistors on order. I will report my findings when I test.

[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

[TA_C10]

In case you haven't seen this video, check it out, guy does a great job explaining the different relay setups and also demonstrating them.

https://youtu.be/nAKnMl1tK8g

.

[Putzer]

TA C10, please post updates and lots of pictures...I am currently having issues with the fan controller from entropy and so have decided to get rid of it and wire it with relays. Looks like I'll be following your lead! If you could post a parts list too, that'd be great!

[TA_C10]

I plan on it. I always take a million photos so no worries there. Check out my build thread too soon as I usually put extra detail in over there. I've been out of town lately but hopefully in next 2 weeks I will have more updates.

I have all my relays wired up at this point, last thing to do is wire in the resistors, diodes, and trinary.

[TA_C10]

Originally Posted by Putzer

TA C10, please post updates and lots of pictures...I am currently having issues with the fan controller from entropy and so have decided to get rid of it and wire it with relays. Looks like I'll be following your lead! If you could post a parts list too, that'd be great!

Here are the parts I ordered for the diodes and resistors. I have more information coming soon. Stay tuned.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[Putzer]

Originally Posted by TA_C10

Here are the parts I ordered for the diodes and resistors. I have more information coming soon. Stay tuned.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Thanks dude

Have you been able to install/test your setup yet?

[TA_C10]

Ok guys, go check out my build page for extra updates and pictures(post 562, soon I will have a few pics of the fuse box and dist blocks). Basically I have it all wired up now but not tested yet. So stay tuned for that.

But I will post my custom wiring diagram here, you can see the changes I made at the bottom of diagram.

After thinking about my fan wiring, I figured out instead of splitting the trinary ground wire close and putting a resistor and diode on each wire separate and connecting to each low and high side trigger connection for the relays, I made the split in wires “after” the resistor and diode so I only needed one.

[dayj1]

Originally Posted by TA_C10

After thinking about my fan wiring, I figured out instead of splitting the trinary ground wire close and putting a resistor and diode on each wire separate and connecting to each low and high side trigger connection for the relays, I made the split in wires “after” the resistor and diode so I only needed one.

You had it right the first time. Now you've just connected the low and hi triggers together. So, you'll only have high speed (the fans will never come on at half/low speed).

[TA_C10]

What's the difference from my first diagram and the last? They both hit the low and high triggers via the AC trinary switch. Only difference is I used 1 set of diodes/resistors instead of 2 sets. Right?

This is only the trinary connection. Low and high still get triggered normally by the PCM. I just put resistance on the line so the PCM doesn't see ground when trinary kicks.

Let me know if you see a flaw I'm not seeing.

[dayj1]

Originally Posted by TA_C10

What's the difference from my first diagram and the last? They both hit the low and high triggers via the AC trinary switch. Only difference is I used 1 set of diodes/resistors instead of 2 sets. Right?

This is only the trinary connection. Low and high still get triggered normally by the PCM. I just put resistance on the line so the PCM doesn't see ground when trinary kicks.

Let me know if you see a flaw I'm not seeing.

Forget about the trinary switch, the resistors, and the diodes for a moment as they’re irrelevant to the issue that I’m pointing out. In your last diagram, you are directly connecting the low speed trigger wire and the high speed trigger wire together (the connection that you drew that loops around the pcm). That’s the problem.

[TA_C10]

Yep, your right, I see it now... Back to original

.

[dayj1]

Originally Posted by TA_C10

Yep, your right, I see it now... Back to original

.

One other thing regarding your 10 amp circuit that you're using for the relay triggers is to make sure that you use an ignition circuit instead of a battery (always on) circuit. It doesn't matter when you're only using the PCM for fan control. But, when you add the trinary switch, it can turn on the fans when the vehicle is off if the coil power is connected directly to the battery. I've wired a few dozen LS swaps over the years and I've personally had 3 or 4 trinary switches go bad and stick shut. That'll activate your fans and run your battery down.