I have a Honda Foreman 400 , 1997 year model with what I think is a fan problem. I removed the front fenders to access the fan control unit as the "Clymer Manual" suggests. I did the book tests, I have power to the fan control unit. I read about 14,500 ohms from the wire going to the the temperature sensor on the block, and ground. The book says 9,500 to 10,500 ohms is normal. Could the temp sensor be out of specs? Can someone help me with the location of the temp sensor so I can remove it and do the test where you put the sensor in hot oil and measure resistance? To get to the temp sensor do you have to remove the rear fenders? I guess oil will leak out which is ok, I need an oil change.

The fan works, I connected 12 volts to the fan, and it works.

When I drive it, the oil temperature light does not light up. Will the oil temp light come on if the fan control unit is not working and the oil temp gets high?

Thanks for the help.

 

Here are the Honda tests .. The thermosensor is at the bottom rear of the engine .. Remove the wire from the thermosensor and ground it , the fan should start ...

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The fan control unit will not only take the signal from the sending unit and turn on the fan, it will also turn on the oil temp light on the instrument panel. Signs of the controller being bad is the temp light flickering while at an idle, or the fan not kicking on and the oil temp light will be on. One flaw in the controller is if it is really bad the fan will not run and or the oil light not come on at all when the unit is overheated. I have rebuilt a number of 400 engines from this happening and piston/cylinder damage being a result.
Reguardless, I have replaced a number of fan controllers over the years as I have noticed the signs of failure during routine maintanance on these quads. Guess You could say I have saved my customers thousands and thousands of dollars in repair bills.

----- Gimpster -----

 

Thanks for the reply Gimpster and HondaMechanic. The pics out of the manual are helpful, much better than the Clymer book. Can you give me any further hints about locating the sensor? Is it on the right of left hand side of the unit? Foot brake side or gear shift side? Are there any extra covers that need to be removed to access the sensor?

Thanks again.

 

Almost centered at the bottom rear , it can be hard to see with the skidplate ..In the picture you can see the reverse lock-out lever and the reverse cable holder ..

 

I removed the skidplate and found the sensor. I turned on the ignition, and placed the blue wire from the fan control unit against the engine block. The fan came on. So that tells me the sensor may be bad. I will do the oil test this weekend. Thanks for all the help.

 

Hi guys I have been having trouble with my 400 fan unit as well my fan won't work have tested the fan unit and fan run ok when disconnect from unit my oil light stays on most of the time it does not flicker at idle I tried your test by disconnecting oil sensor and grounding to motor but no joy fan still did not run would this mean I have a broken wire back further hope you maybe about to shed some light

 

hey my 400 foreman has the cooling fan running all the time, i found the oil senser and ran the wires to a connector and unpluged it and the fan still ran, im thinking it is the cooling module but not real sure, i think i may just let it run all the time im running it do you think it would hurt anything to do that

 

The fan running all the time is no big problem. We have just taken an early 450 in part exchange that has had the fan running with the ignition for years. The wire to the temperature switch is just a single one that the switch earths when hot so, if you disconnected it and the fan still runs, it must be shorting to earth in the loom somewhere.

 

my unit is a 2001 honda foreman trx 400 the wire i disconnected was on the left side( me sitting on the bike) at bottom of back side of engine it has 3 wires going to a connector, i thought that was my oil temp sensor, can you tell me where is the single wire your talking about, thanks so much