Switched Power for Electric Fan Relay

[Bruce Wingate]

Finishing up installing dual electric fans and hit a small snag with wiring the relay. The relay needs a switched Power source. I would like to find one in the engine bay rather than going through the firewall to the fuse block. I would call this the trigger or sensor wire. It is not the power for the fans.

I think I have the options: the choke circuit, the exciter wire for the alternator (my second choice), or the wiper motor Power. My top choice though is the power wire going to the trinary switch. I have to check with vintage air to see if this is possible.

I don't want to run power right from the battery for this. The fans running after the truck is turned off makes me worried about draining the battery.

Does anyone have any suggestions or preferences?

 

[AKguy]

I cheated and used my Holley Sniper trigger leads, but I cannot see why the choke feed would not work well.

 

[Doppleganger]

Audi used to have a fan timer relay that was run off the battery and would run a fan for either 3 min or to a certain temp. We used these on other cars, in particular turbos for heat soak.

So off the battery in a controlled or timed curcuit wouldn't be bad. Fans can be a big draw so not sure I'd use the wiper circuit.

 

[AuroraGirl]

Finishing up installing dual electric fans and hit a small snag with wiring the relay. The relay needs a switched Power source. I would like to find one in the engine bay rather than going through the firewall to the fuse block. I would call this the trigger or sensor wire. It is not the power for the fans.

I think I have the options: the choke circuit, the exciter wire for the alternator (my second choice), or the wiper motor Power. My top choice though is the power wire going to the trinary switch. I have to check with vintage air to see if this is possible.

I don't want to run power right from the battery for this. The fans running after the truck is turned off makes me worried about draining the battery.

Does anyone have any suggestions or preferences?

wipers my vote. Because that system could go for some improvements as it is and its wide open the wire just gotta probe for it. The fans should be wired to a constant hot with temp being the main trigger and AC engagement being another and some people have a 30 second run when turned off setting but thats more for icing on the cake not the main cake composition itself.

 

[AuroraGirl]

Audi used to have a fan timer relay that was run off the battery and would run a fan for either 3 min or to a certain temp. We used these on other cars, in particular turbos for heat soak.

So off the battery in a controlled or timed curcuit wouldn't be bad. Fans can be a big draw so not sure I'd use the wiper circuit.

if the wiper is just a switched power for a relay trigger, it shouldnt be bad i would think

EDIT: OP, to be clear, you are trying to power a trigger for a relay to send power which is coming from the battery, correct? I think that is what you said looking at it.

 

[Bruce Wingate]

Audi used to have a fan timer relay that was run off the battery and would run a fan for either 3 min or to a certain temp. We used these on other cars, in particular turbos for heat soak.

So off the battery in a controlled or timed curcuit wouldn't be bad. Fans can be a big draw so not sure I'd use the wiper circuit.

This is power for the switching part of the relay which I think is pretty low draw. Fan power is from the battery.

 

[AuroraGirl]

This is power for the switching part of the relay which I think is pretty low draw. Fan power is from the battery.

perfect. its still normally a constant power in gm vehicles but that works, too. it just wont run the fan if you overheat and turn the key off, which isnt going to be often hopefully and im not sure how much it would change the outcome either. Wiper is still my vote because you can use a fuse tap and run a wire like that and not even disturb the wiring.

 

[dsteelejr]

Not sure what year your square is, but just so you are aware at least some years, if not all, wipers were on the accessory circuit with the radio, so your relay will be powered with ignition on and accessory power.

 

[AuroraGirl]

Not sure what year your square is, but just so you are aware at least some years, if not all, wipers were on the accessory circuit with the radio, so your relay will be powered with ignition on and accessory power.

:O good catch

 

[Grumpy]

I would go with Doppleganger on this.
Whatever you do, make certain you have a fuse as close to your power source as possible. You do NOT want six feet of fusible link to melt.

 

[Bruce Wingate]

Vintage Air tech support got back to me and said using the wire going from their system to the trinary switch is OK - I just have to figure out if that wire only has power when the AC is on. I'll know this weekend hopefully when I finish the main connections and try to start the truck. [In case anyone is worried, I plan on finishing the alternator, power and grounds and testing that before I start tapping in the fans and the AC so I only have one problem at a time.]

 

[Bextreme04]

I used three relays since I have a dual electric fan system. I used the 2008 Truck electric fan wiring as a guide. It allows me to run a low and a high speed. I ran the low speed trigger from the AC system(that would be your trinary switch trigger) and high speed from the temp switch installed in passenger side head. Power is from an ignition circuit relay that is triggered by the wiper motor wire that is powered on from the accessory circuit. I'm using this waterproof fuse and relay box from amazon. https://www.amazon.com/gp/product/B08KHVHLL5/ ... it actually seems to be really good quality. I also have flyback diodes and an on-off-on switch installed to allow me to manually control the fans. I can post a wiring diagram if you want... but its a bit "back of the cocktail napkin" right now.

 

[Bruce Wingate]

I think I bought that same relay box. My plan is a little simpler: 2 fans each with their own relay with both triggered by either the trinary switch from the AC or the temp sensor i put in the water neck. Ultimately, I would like the fans individually controlled by a fuel injection system, but that is down the road a piece.

I know the location of the temp sensor is not ideal, but it is convenient and my readings should be "close enough."

 

[Bextreme04]

I think I bought that same relay box. My plan is a little simpler: 2 fans each with their own relay with both triggered by either the trinary switch from the AC or the temp sensor i put in the water neck. Ultimately, I would like the fans individually controlled by a fuel injection system, but that is down the road a piece.

I know the location of the temp sensor is not ideal, but it is convenient and my readings should be "close enough."

The third relay is what gives you the low/high capability. It doesn't actually carry much current, but just switches the fans from series to parallel so that you go from 6v for low to 12v for high. I use the low for AC, since it would be always on, and high for the temp. I wanted a switch to be able to turn them off if cruising on the highway or getting into some nasty mud/water and also wanted to have the option to lock them on if my temp sensor craps out or isn't triggering on at the right temp. I'm also going FI in the near future, so I wanted it wired right for the Fan1/Fan2 output that the 0411 ECU's would output normally.

 

[Bextreme04]

Here’s roughly what I did. It’s got a few scribbles on it where I’ve modified the stock wiring diagram to account for no ecu control and my manual switch on the high side apply.

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