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Discussion Starter · #1 ·
I’d like to wire in a remote fan switch on my 01 TRX400FW. Anyone have a wiring diagram or a quick how-to on doing this properly?

I’m assuming that the sending unit that normally turns it on goes to ground when active correct??

Thanks
T
 

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It would be easy to figure out. Use a meter and see if there is 12v on the fan when it is off. If there is, then on the other fan connection short it to ground and see if it comes on. If it does, then put a dpst switch in line, common to the fan, one leg to the sending unit, the other to ground.

That will make the switch control the fan manually or allow the sending unit to control it.

If the sending unit supplies 12v, do the same thing except instead of ground on the second leg of the switch, make it 12v.
 

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Discussion Starter · #3 ·
That's my intentions but I figured that maybe someone has already done it and share the details. That would make the job that much faster...
 

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It would make it easier, but I would always recommend that you test it for yourself just to be sure.

I remember a time when I was a teenager installing a radio in my friends car. I had a meter, could easily have tested what all the wires were, but my friend grabs and wire and says "what is this, ground?" It was green, so I hooked it up as ground. It wasn't ground and it fried the radio. Oops.
 

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I remember a time when I was a teenager installing a radio in my friends car. I had a meter, could easily have tested what all the wires were, but my friend grabs and wire and says "what is this, ground?" It was green, so I hooked it up as ground. It wasn't ground and it fried the radio. Oops.
Yeah, I agree. A lot of automobiles built anymore, don't use the normal colors for hot and ground. I think Toyota is one of the worst ones for this.
 

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Try wiring a BOBCat Skid loader...lol all the control wires are WHITE they have numbers etched into the sheathing every 6 or 8 inches..lol and the wires to the engine are brown. lol the main harness to the control panel has color coded wires. oh what fun
 

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The thermo sensor does ground the fan circuit, but it goes through a fan control unit. It would probably work the way you want to do it, but the only problem is that the oil temp light would probably stay on all the time. Here is a wiring diagram for the 400 Foreman.

 

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If I recall the oil temp light doesn't come on with the fan, but if it comes on after you wire up that switch, then you can put a large diode in line to eliminate the light from coming on when you turn the fan on manually.

ADDED: Actually helmet, the light won't come on. The old circuit will be open and the fan will be isolated with the new switch, so it should be OK.
 

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Agree ^^^ you can even install a relay or the diode as added precaution
 

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If I recall the oil temp light doesn't come on with the fan, but if it comes on after you wire up that switch, then you can put a large diode in line to eliminate the light from coming on when you turn the fan on manually.
I think it will if you ground the circuit. I think the thermo sensor is a variable sensor and it works like a variable resistor, it doesn't just have on or off. The resistance changes with temperature, so when the oil temp starts getting hot, the control unit will switch the fan on. When the oil temp gets even hotter, the control unit will turn the oil temp light on, as well. So if you just ground the wire, the control unit will think the engine is extremely hot and turn the fan and the oil temp light on.
 

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But he's going to open the circuit, not just ground that connection. At least that's what I thought he was going to do. Break the connection and put a switch in that makes the original or makes the new ground, but not both at the same time.
 

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I think I understand what you mean now. You're saying he can run a separate ground wire through a switch to the fan. I see now. I was thinking he wanted to just ground the wire that runs to the thermo sensor and put a switch there. Yeah, running a new ground wire through a toggle switch directly to the fan, bypassing the control unit will work.
 

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Yeah, but he has to also switch the original wire.

Remove the original wire from the fan. Tie the common of the switch to the fan, the original wire from the sensor to one leg of the switch, and ground the other leg of the switch. With the switch in one position, its like it was originally. In the other position it grounds the fan.
 

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Yeah, but he has to also switch the original wire.

Remove the original wire from the fan. Tie the common of the switch to the fan, the original wire from the sensor to one leg of the switch, and ground the other leg of the switch. With the switch in one position, its like it was originally. In the other position it grounds the fan.
Yes, Pain, you're right. That will work. Sorry, I just misunderstood you earlier.
 

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Discussion Starter · #16 · (Edited)
Judging by the wiring diagram on the first page of this thread, adding a switch to the ground wire won't do anything. Looks like I need to put the switch on the feed wire from the fan control unit and then to a 12v power source....?

Anyone wanna back me up on this??

"Pain" is that what you're telling me to do?

T
 

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I agree, in the diagram it looks like the ground is hardwired and the 12v for the fan is controlled through the control unit.

So yes, given that, then of course you want to switch the 12v and not the ground as previously stated. Everything else said remains the same, you're just switching between either hard wired direct 12V OR the original control unit connection.
 

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