Fan

[Wormy 60]

Ok guys! Need a little help here. I’m not the greatest on wiring but I know the basics. I want to know if my fan is working on my trx450es before I just get on it and tear out after getting it back up and running. My display is not working currently. Have to get  AKATV to remedy that for me in the near future. But wondering if there is and easy way to test the fan and also a way to test if it is going to cut on at a certain temp. Any and all help is always appreciated. I hate to keep asking such rookie questions but I guess that is what this site is for. 

[AKATV 850]

Pull the blue wire connector apart behind the right rear fender, its located close to the other wire connectors

Ground the harness side of the wire to bare metal or to the negative terminal and with the key in the "on" position the fan should come on as well as

the oil temp light

if fan does not come on you most likely have a bad fan control module or a bad fan motor, you can put 12v directly to the fan to test the fan

Does your temp light come on for 2 seconds and then go out and stay out when you first turn the key on? This is a self test for the fan module

 If not, then I would suspect a faulty fan control module 

You can bake them in an oven at 425-450 degrees for 6-7 minutes to reflow broken  internal solder joints which are the main cause for most module issues

Sounds a little hokey but have fixed many of them this way and some are still working 15 years later

Edited November 8, 2021 by AKATV

[shadetree 5,977]

the easy way to test the fan: unplug it from the harness, on that model, left front side of fuel tank, look for two bullet connectors, one will be blue, the other will be green. unplug them, connect them to 12 volt dc ( a battery ), if fan is good  ?, it will kick on. second way : right side of atv, behind right side panel, where all the connectors are snapped into the frame there is a single blue bullet connector, it leads to the oil temp sensor at very bottom of rear engine. unplug it, on the harness side of connector , turn key on, ground the connector to a good ground source, when you do this, the fan should kick on. depending on if fan is good or not ?, will mean if you are out riding hard, and the fan never kicks on, and you know it is good ?, this tells me and you that the fan control unit or the oil temp sensor that i spoke of earlier in this post is bad. DO NOT UNSCREW OIL TEMP SENSOR UNLESS YOU ARE VERY FAST AT PUTTING NEW ONE BACK IN ?, or you will lose a crap load of engine oil..lol. its best to remove the oil temp sensor with the bottom skid plate off, because its a royal pain to get to the oil temp sensor with the skid plate not only installed ?, but also with the skid plate off !..lol. it takes some tricky stabbing to get the wire back onto the end of the sensor even with the skid plate off !. i highly say drain the engine oil before you go unscrewing the oil temp sensor if you must replace it !!!!!.

[Goober 1,555]

Absolutely what they said ^^^. Check the Oil Cooling System diagnostics 

 

if you get a steady oil light, the oil light continuously flickers or the oil light never comes on, this signals a failure of the Fan Control Unit or harness connections. There’s some testing involved.
 

Then test the resistance of the oil temp sensor. If resistance exceeds 10.5 KOhm, the sensor will not turn on the fan at the target cooling temp of 100C.

 

on my 450S, the oil light constantly flickered. I replaced the oil temp sensor and the FCU, which BTW the FCU was $195.

check the fan. The oil cooling diagnostics explain how to jump a hot lead to the fan power wire.

Edited November 9, 2021 by Goober

[Fishfiles 20,147]

[Fishfiles 20,147]

 ^^^ Toggle switch can be used as an over ride or/a  on-off  switch  ^^^ 

[shadetree 5,977]

4 hours ago, Fishfiles said:

 ^^^ Toggle switch can be used as an over ride or/a  on-off  switch  ^^^ 

see, what you fail to understand is, if the fan control unit is bad or going out ?, it shuts the c.d.i. down, so by adding a toggle switch to the atv, all you are doing is getting power straight to the fan, bypassing the fan control unit. in the long run, he will be stuck miles from home. need to edit this..the toggle switch will work on the 450's..my statement here ONLY applies to the old school 350's..sorry bro !.

[AKATV 850]

58 minutes ago, shadetree said:

see, what you fail to understand is, if the fan control unit is bad or going out ?, it shuts the c.d.i. down, so by adding a toggle switch to the atv, all you are doing is getting power straight to the fan, bypassing the fan control unit. in the long run, he will be stuck miles from home.

In all the machines I’ve worked on (Foreman 450) I’ve never seen the FCU shut down spark to the CDI

It would make sense for it shut it down if you had a cooling failure, but I’ve never seen it happen and don’t believe it’s capable of doing so

I don’t even see  on the schematics on how that would happen as they appear to be two completely separate circuits.

That’s just from my experience and I’m always learning new things along the way-

can you school me on how this happens?

Did you possibly mean when the FCU is going bad it shuts the cooling fan operation down and not the CDI?

 

Edited November 9, 2021 by AKATV

[shadetree 5,977]

4 minutes ago, AKATV said:

In all the machines I’ve worked on (Foreman 450) I’ve never seen the FCU shut down spark to the CDI

It would make sense for it shut it down if you had a cooling failure, but I’ve never seen it happen and don’t believe it’s capable of doing so

I don’t even see  on the schematics on how that would happen as they appear to be two completely separate circuits.

That’s just from my experience and I’m always learning new things along the way-

can you school me on how this happens?

Did you possibly mean when the FCU is going bad it shuts the fan down and not the CDI?

 

crap, i'm stuck on the old 350 models..my bad..brain is fried right now..lol. i need to be in the woods !..lol

[AKATV 850]

Ok Shade thanks for clarifying -just wanted to make sure I wasn’t missing something 

I need some woods time too….lol

Edited November 9, 2021 by AKATV

[Fishfiles 20,147]

1 hour ago, shadetree said:

see, what you fail to understand is, if the fan control unit is bad or going out ?, it shuts the c.d.i. down, so by adding a toggle switch to the atv, all you are doing is getting power straight to the fan, bypassing the fan control unit. in the long run, he will be stuck miles from home. need to edit this..the toggle switch will work on the 450's..my statement here ONLY applies to the old school 350's..sorry bro !.

Lol.    see what you fail to understand. Is you need to do a better job of reading and comprehending  the post  as  he has a  TRX450.  They got a couple of things they call that ,  drive by media is one or getting old the other We’ll have to edit the edit. 

[Melatv 797]

Hi: I have never found a ATV that the Fan Motor Control would shut down the CDI -- that would be a unsafe thing to do -- can you see a ATV climbing a ice or slipper hill and the bike shut off -- when needed the power to get to the top safely what going to happen to the ATV & ATVer?

 

As far as the 86 350 the is no connection (no Connection) between the Fan Motor controller and the CDI 

Some of the newer ATV will go into limp mode -- but not shut down

 

The Fan Motor Control only controls the Oil Temp Light and Fan motor when the Oil Temperature Sensor is calling for the Fan to turn on.

[shadetree 5,977]

On 11/9/2021 at 11:45 AM, Fishfiles said:

Lol.    see what you fail to understand. Is you need to do a better job of reading and comprehending  the post  as  he has a  TRX450.  They got a couple of things they call that ,  drive by media is one or getting old the other We’ll have to edit the edit. 

LOL, i did edit it, i was asleep at the wheel..lol.

[shadetree 5,977]

12 minutes ago, Melatv said:

Hi: I have never found a ATV that the Fan Motor Control would shut down the CDI -- that would be a unsafe thing to do -- can you see a ATV climbing a ice or slipper hill and the bike shut off -- when needed the power to get to the top safely what going to happen to the ATV & ATVer?

 

As far as the 86 350 the is no connection (no Connection) between the Fan Motor controller and the CDI 

Some of the newer ATV will go into limp mode -- but not shut down

 

The Fan Motor Control only controls the Oil Temp Light and Fan motor when the Oil Temperature Sensor is calling for the Fan to turn on.

hmmm..according to the honda service manual in the tech section for the old trx350's, it clearly states that in the event of an over heating ?, the fan control unit shuts the c.d.i. down, i'll have to dig my manual out when i get a chance, and read it again.

[shadetree 5,977]

here it is, it only applies to '' after '87 models on the 350's.

[Melatv 797]

18 minutes ago, shadetree said:

hmmm..according to the honda service manual in the tech section for the old trx350's, it clearly states that in the event of an over heating ?, the fan control unit shuts the c.d.i. down, i'll have to dig my manual out when i get a chance, and read it again.

That is the Fan motor not the engine

Section 20-2

Edited November 10, 2021 by Melatv

[shadetree 5,977]

10 minutes ago, Melatv said:

That is the Fan motor not the engine

yes..but it says..'' cuts power to engine '' so..in order to do that..it has to go through the c.d.i. right ??. or is it talking about the fan motor ?..it does not say clearly huh ?.

[Melatv 797]

Just now, shadetree said:

yes..but it says..'' cuts power to engine '' so..in order to do that..it has to go through the c.d.i. right ??.

Where do you see that in the service manual?

[shadetree 5,977]

Just now, Melatv said:

Where do you see that in the service manual?

its on 22-3 in my service manual, maybe i am reading it wrong ?.

[Melatv 797]

I have the same service manual -- Fan motor -- section 20-2

[Melatv 797]

Section 20-2

[shadetree 5,977]

13 minutes ago, Melatv said:

Section 20-2

yeah, i'm gonna say they are talking about the fan motor, not the engine motor.

[Wormy 60]

Ok here is where I stand. I have taken the blue and green bullet connectors off and powered them and the fan turns on. Then I  unplugged the single blue one by the pull start and ground it and the oil temp light will come on but not turn the fan on? Is it not grounded good or could the oil temp sensor be bad?

[AKATV 850]

Wormy I just replied to the text you sent me for the same message..

 

(I know this is a goofy thing to ask but did you plug the two wires in for the fan before you tested it with the blue wire?)
 if you're grounding the blue wire on the harness side and the red light comes on but no fan and since you’ve already tested the fan motor directly, it is most likely the fan control unit which is the little black module that's up under your front fender right beside your CDI black module you'll know it's the fan module because it has a green connector port on it
If you have a helper while you're grounding the wire with the key on, have somebody give it a couple raps with the handle of a screwdriver on the module and see if your fan comes on 
if it does you probably have a fractured solder joint inside which is pretty common just unplug it pull it out stick it in the oven at 450 for 7-8 minutes or so
That will reflow the solder joints if that's your problem
After 20 years of heat and vibration they break down
I fixed a lot of them that way -some of them working 15 years later 
if it doesn't fix it -it's easy enough to pick one up for 25 bucks on eBay eBay

Edited November 10, 2021 by AKATV

[Wormy 60]

Yes, I plugged the two wires by the gas tank back in before testing the single blue wire by the pull start. I don't have a battery in the ATV but have been using a jump box to power it. When I turn the key on the red light comes on for a couple seconds and then turns off. When I first started to ground the back wire, the red light would come on and I could hear static like noise coming from the area where the two plugs are by the gas tank. Now i cannot get it to make that sound again? Could that have been the fan control unit? Let me know what I need to try now. P.S. - the single bullet connector behind by the pull start is a pain in the a$$ to get to and put back together.