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hellenikboy

Thermofan Wiring Diagram

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Hey guys,

So I have been searching the forums to try and find a wiring diagram to make the most out of my el thermofan install for my 351 XE.

There were a few useful diagrams that I found but very few made use of the two fan speeds on the thermofans and an automatic turn on when the AC is on.

I also wanted to use a thermofan switch because it looks cleaner than having the rod in the upper radiator hose.

So I decided to draw up my own diagram, I spent a bit of time drawing it and I think it will work but if anybody who knows a bit about auto electrics can check it to make sure its all good to go.

I plan on writing a DIY "how to" on the forum using this diagram when I have finished the install.

Thanks

 5902914d5829a_Thermofanwiringdiagram.thumb.png.b8e41a14599e846e0b4e7b5fae076410.png

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Yea it is a bit complicated. I wanted to take advantage of low and high speed plus I have AC so the fan needs to come on when that is running.

I could make it simpler by only having high speed. That would remove two relays out of the circuit.

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Try this.
When low speed is active relay one energises and feeds power to fan 1, which then runs via relay high's relaxed state pole and into fan 2. The fans run in series.

When high speed is active, relay ground sends Fan 1's negative to ground, and relay high switches poles, sending 12v to fan 2.  Both fans are run in parallel. 

The piss yellow diode may not be needed, It is there to ensure that relay low is switched when high speed is on.

The input from A/C is protected with a diode to prevent 12v flowing back into the A/C switching unit, in case whatever is switching that has a grounded off state.

 

I choose to use constant 12v rather than switched as this will prevent the fans from failing at the loss of a single relay. If relay low or ground fails you can still get Fan 2. If relay high fails you can still use Fan 1

 

Alternatively you can run the AC signal into the low speed switch, it's probably not necessary to run the fans at high speed for the a/c. Be aware that the a/c signal needs to turn off when the car is moving, and on when the car is stopped. Otherwise your fans will never turn off when the a/c is on regardless of forward speed.

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Im using the same as NZXD.
I have both running at the same time and it works well but i dont have aircon.

Where did you pick up the 12v ignition source from?


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Agreed, fans not really required when moving. Maybe a thermoswitch, so as coolant temp goes down, fans stop.?

Or a manual switch on the dash, lights up when coolant is hot or A/C is on, light goes out.......turn it off.  Bit off a pain.

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You could try a sail switch.
It's a micro switch with a large surface area attached to its actuating lever. Air blowing against it actuates the switch. If you inserted this into the oncomming airstream, and did a little R+D you could make this act as a sensor to turn the fans on, when AC is enabled, Whenever there is insufficient forward airflow. I'd recommend using a delay circuit though, so as not to cause constant false triggering of the fans. And ensure you dontt put it in the path of the airflow created by the thermo fans, as this would create a latching circuit.

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Whats a good 12v igniting source to use for thermos in the engine bay?

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Coil + to relay terminal 85, then from 86 a coolant temp switch to earth. Supply from batt + to 30 with a fuse to suit, 87 to fans.

If running a ballast resistor, you might have trouble triggering the relay. You could instead feed off windscreen wiper supply.

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Coil + to relay terminal 85, then from 86 a coolant temp switch to earth. Supply from batt + to 30 with a fuse to suit, 87 to fans.

 

If running a ballast resistor, you might have trouble triggering the relay. You could instead feed off windscreen wiper supply.

 

Sent from my CPH1607 using Tapatalk

 

Thanks for that, will revert to this plan if current setup does not work, I pinched the 12volt ignition from the second washer bottle pump plug, hopefully this works was nice and easy and isn't powering anything else

 

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Hey all, sorry for bringing up a slightly old thread. Got a couple. Of quick questions for you all.
1. What gauge wire are you using for wiring up the fans?
2. What can be done to delay the fans coming on when first starting the car? The issue I've got (comes up at the drags alot) is shut the car off when still hot. Go to refire car when it's still got and fans kick in straight away before car has a chance to start. Fans draw to much power car won't start battery dies.

Any suggestions?

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Wire needs to be decent, i'd go 2.5mm and 40A fuse.

 

You could cut fan supply through a changeover relay connected to your oil pressure lamp. Changeovers have two outputs 87 and 87a. Connect power to 87a (normally closed) and when you turn on ignition, oil pressure lamp comes on, relay powers up and 87a goes dead. Start engine, once oil pressure lamp goes out, relay switches off and 87a goes live again, turning fans on.

 

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Wire needs to be decent, i'd go 2.5mm and 40A fuse.
 
You could cut fan supply through a changeover relay connected to your oil pressure lamp. Changeovers have two outputs 87 and 87a. Connect power to 87a (normally closed) and when you turn on ignition, oil pressure lamp comes on, relay powers up and 87a goes dead. Start engine, once oil pressure lamp goes out, relay switches off and 87a goes live again, turning fans on.
 
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Great idea I'll give that a go thanks alot.

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