[Art Schneider]

I rode my 2008 Honda Rancher 420 yesterday and it overheated twice (light came on) after riding for approximately 10 minutes. I took it home and pulled the thermostat out, and tested it in near boiling water, and watched it open, so I don't think it's the thermostat. The coolant appeared to be full prior to going on the ride. One thing that I didn't pay attention to, that I wish I would have, is if the fan came on or not. Is there an easy way to test that? The land that I drive the atv on is 2 hours away, so I'm hoping I can get it fixed before hauling up there again.

I'm open to any other suggestions!

 

[SamUK]

Have you checked the motor oil? What colour is it? Is the coolant clear and as it should be? Any evidence of water/oil contamination?

 

[Art Schneider]

Have you checked the motor oil? What colour is it? Is the coolant clear and as it should be? Any evidence of water/oil contamination?

Hi Sam, I changed the oil just before this trip, and it still looks like brand new, although I didn't drain it, just going off the dip stick. No evidence of coolant in the oil, or oil in the coolant. The coolant looked a little too green. I suspect that the mix was heavy on coolant, low on distilled water.

 

[Art Schneider]

I should also mention that I looked at the radiator, and it doesn't have mud, or anything else in it. The blades aren't bent, and I can easily see light through it.

 

[SamUK]

I should also mention that I looked at the radiator, and it doesn't have mud, or anything else in it. The blades aren't bent, and I can easily see light through it.

I’m not overly familiar with the 420’s but I’d check the manual, I assume it’s fused, start there. Next I’d disconnect the fan from the harness and hard wire it to a battery just to confirm it works.
Failing the above options I’m pretty certain that the fan is controlled by the cdi or an fcu, which would mean a replacement is required.

 

[Art Schneider]

I should also mention that I looked at the radiator, and it doesn't have mud, or anything else in it. The blades aren't bent, and I can easily see light through it.

I’m not overly familiar with the 420’s but I’d check the manual, I assume it’s fused, start there. Next I’d disconnect the fan from the harness and hard wire it to a battery just to confirm it works.
Failing the above options I’m pretty certain that the fan is controlled by the cdi or an fcu, which would mean a replacement is required.

Looks like you were dead on with the fuse! I wish I had checked there first, looks like I don’t even have a fuse for it!

 

[Art Schneider]

And if I'm reading that right, I also have a 30 where a 10 should be for the ignition.

 

[Goober]

Check to make sure you didn’t install the oil. Filter backwards

 

[Art Schneider]

I put the fuse in for the fan, but after running it for a few minutes, I never saw/heard the fan turn on. I also verified that the oil filter is in correctly.

I saw on another post someone had a similar issue, and by unplugging the ect sensor, their fan came right on. I'm not sure where this sensor is...

 

[Art Schneider]

I think I found it. And I just unplugged it.

 

[Art Schneider]

The fan does not come on when I unplug it and turn the key to on, or run the ATV. I tried running a wire to jump the plug, and it made no difference, but I'm not 100% sure that I made good contact.

Trying to figure out a way to run power to the fan to get it to come on and verify that it works. It does turn freely by hand.

 

[mrbb]

you should be able to disconnect the fan and just add direct power to it to make it run(or show it doesn't work)
should be a test for this in the service manual?

also, something else to think about,
JUST cause your coolant level is FULL<> doesn't mean the coolant is any good.
so, when was the last time you drained and flushed the system and add FRESH new coolant(50/50 mix I would think is correct here too, not just pure coolant)
and also, if you live in a very HOT area, there is better coolant options out there that will help it run cooler, as will GOOD syn oil in the motor will too!
so, might be something to look into if your over heating,
also might be time to READ your spark plug and make sure its not something else running you HOT!

 

[Art Schneider]

you should be able to disconnect the fan and just add direct power to it to make it run(or show it doesn't work)
should be a test for this in the service manual?

also, something else to think about,
JUST cause your coolant level is FULL<> doesn't mean the coolant is any good.
so, when was the last time you drained and flushed the system and add FRESH new coolant(50/50 mix I would think is correct here too, not just pure coolant)
and also, if you live in a very HOT area, there is better coolant options out there that will help it run cooler, as will GOOD syn oil in the motor will too!
so, might be something to look into if your over heating,
also might be time to READ your spark plug and make sure its not something else running you HOT!

I see the blue/Green wires coming out of the fan, but they go up and get kinda lost into other wires... I'm hoping I don't have to take the front plastics off....

I replaced the coolant when I took the thermostat out and tested it. It does have Honda Synthetic 4 stroke 10W30 motor oil that I put in in March.

I'll take a look at the plug. It was replaced a few months ago (just routine maintenance, I wasn't sure how old it was).

 

[Art Schneider]

I took off the plastic in the wheel well and found that the fan on mine was connected by twisting the wires together with electrical tape covering it. I ran wire from the battery to the junction of these wires and the fan ran. I think it must be the sensor. Going to order one tonight.

 

[SamUK]

I took off the plastic in the wheel well and found that the fan on mine was connected by twisting the wires together with electrical tape covering it. I ran wire from the battery to the junction of these wires and the fan ran. I think it must be the sensor. Going to order one tonight.

It stands a chance that the issue could be from a poor connection, you say the fuse was blown yes?
If the wires were twisted together it may be arcing and blowing the fuse and/or not passing enough current (amps/volts).

Connect those wires properly, solder them or fit a new plug, ensure the connection is as good as OEM and see how that works for you.
I wouldn't be buying parts until I'd fixed those wires, it may be a waste of hard earned cash