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I started a new thread cause I wondered if anyone else might chime in on this issue. This is for the '86 and other years that apply, TRX oil temp sensor, not kicking the fan on till about 300 deg.

Was talking with a neighbor this evening about this and we got to wondering if an external temp sensor could be mounted somewhere to kick the fan on a bit earlier?

I am not too familiar with things like that, but it sounds reasonable. To me anyway, not like that means a whole lot.
 

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I had forgotten but... shadetree mentioned way back that he had found a solution for one of his motorcycles by buying a sensor (from an auto parts store I think?) that was made for a different motor/application and simply swapped the new sensor in. You might want to look into that option... find some that fit into the side cover (or use an adapter) and from there its just a matter of putting a sensor in there having less resistance than stock. It may involve some trial & error testing to get one that kicks the fan on where you want it to, but once you learned which sensor works the best everyone could benefit. I'd do it that way myself if I knew which sensor to buy... I'm a tightwad though.
 

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Have you checked the temp just to be sure? I used an infra red temp sensor/gun when I tested mine.
It's a shame nobody makes a sensor that fits in between the cooling find on the head, I realise the temp sensor would have to be lower operating temperature but I for one would certainly consider buying one.
I have my fan running through a switch and Its always on your mind, a little distracting I find if I'm honest.
 

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Hi: Just do it the simple way -- wire in a toggle switch to turn the fan on and off at will.
The sensor still stays there to turn the fan on also if you don't turn the the toggle switch on. See diagram.
 

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Hi: Just do it the simple way -- wire in a toggle switch to turn the fan on and off at will.
The sensor still stays there to turn the fan on also if you don't turn the the toggle switch on. See diagram.
Mine didn't work at all, hence wiring in the switch. At the time I was wanting to use the ATV, it's undergoing surgery at the moment and she a wiring harness swap so I may well get the fan working on the sensor and also through a switch.
 

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the problem with installing a switch to turn the fan on ?, some ppl forget the fan is on ?, then they have a dead battery !..lol. kinda like some switch the '' kill '' switch off, and forget to put it back in the middle ?, or..turn the fuel off, take off, and it dies..and they don't know why ?...trust me..WE ALL DO STUPID STUFF ..OR WE WILL !..LMFAO.
 
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I've done the fuel tap trick so many times shady! Haha. They always seem to die half way up a good hill climb or just as you enter a good mud hole to ha!
My fan is quite loud so I usually hear it, not forgotten it as yet.
 

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I've done the fuel tap trick so many times shady! Haha. They always seem to die half way up a good hill climb or just as you enter a good mud hole to ha!
My fan is quite loud so I usually hear it, not forgotten it as yet.
lmao, I hear ya..they ALWAYS DIE IN THE WORST PLACE !..LMFAOOO, I can attest to this, was moving my jet ski around my yard/drive way one day, using my '03 trx450fm that I just finished, had it out in the street backing it up, atv died..wth ????..crap..after a few seconds, dawned on me, fuel was shut off !..lmfaoooooo.
 

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the problem with installing a switch to turn the fan on ?, some ppl forget the fan is on ?, then they have a dead battery !..lol. kinda like some switch the '' kill '' switch off, and forget to put it back in the middle ?, or..turn the fuel off, take off, and it dies..and they don't know why ?...trust me..WE ALL DO STUPID STUFF ..OR WE WILL !..LMFAO.
With sensor bypass switch installed -- when you turn the key switch off the fan goes off -- Yes STUPID STUFF if you leave key on without the bike running -- sure the battery will go dead -- so installing the bypass switch is not STUPID STUFF.
 

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the problem with installing a switch to turn the fan on ?, some ppl forget the fan is on ?, then they have a dead battery !..lol. kinda like some switch the '' kill '' switch off, and forget to put it back in the middle ?, or..turn the fuel off, take off, and it dies..and they don't know why ?...trust me..WE ALL DO STUPID STUFF ..OR WE WILL !..LMFAO.
With sensor bypass switch installed -- when you turn the key switch off the fan goes off -- Yes STUPID STUFF if you leave key on without the bike running -- sure the battery will go dead -- so installing the bypass switch is not STUPID STUFF.
if the sensor is working like should ?, then there is no reason to add a switch. also, some owners wire this switch straight to the battery ?, this bypasses the option to kill the fan when the key is turned off. I've seen it done a lot. not everyone takes the time to wire stuff correctly ?, if this was done right ?, then there should not be a switch at all. a simple new sensor installed would solve all this. some ppl don't want to take the time to do it right.
 

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Some like myself just want to switch the fan on before the sensor kicks in. You can wire the switch to the sensor or wire the switch to the green wire on the Fan. The sensor changes resistance as the engine heats up -- the resistance of the sensor goes lower to a point where there fan starts that resistance is wide gap not just a true turn on point for the Fan to start.
Riding a ATV real slow for hours at a time when hunting I prefer to have the Fan running at all times -- also pulling large game animals out of the woods I prefer to have the Fan running at all times.
Some people run there ATV's a long way from home -- leave from the house by bike and bike (100+ Km), not just just a few Km around there house. Just another safety feature if the sensor fails.
 

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I agree with Melatv. A manual switch, even if its never needed, or never used regularly by the operator, is a great option to have on any fan equipped bike.

As they say, an ounce of prevention is worth a pound of cure... that certainly applies to overheating your motor oil. Once a certain high temperature threshold is reached, every motor oil is permanently junk and must be changed out immediately. Those high temp thresholds for motor oils are much lower than many think!

When the operator knows the bike is going to be put to some slow or hard work, they can simply turn the fan on to prevent any potential excessive heat saturation issue from gaining legs. If the fan motor, or the fan control unit ever fail, the operator may be alerted to that problem before damage is done too.

Its got to be done right like though, like Melatv explained with his drawing. It should be a professionally built installation plugging directly into the existing harness plugs, ONLY. Expect no mercy if you're the hacking, cutting, splicing, taping, kind of guy around vehicle wiring harnesses!

I am going to implement both an adjustable fan control kick on AND the manual switch features into mine. I'll also add a tiny indicator light somewhere that glows while the fan is running. I'm convinced my bike will benefit.

Thanks for this thread!
 

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I have my on/off switch wired to a hot wire that is turned on/off with the key...it also connects to a 15A fuse in the rear trunk of the bike. I got tired of trying to find a good working fan relay unit so now I can just run the fan whenever and as much as I want to :icon_ banana:
 

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@PatrickB,

If you ever get a good fan control unit you can add a relay between it and the fan motor to help keep the new controller alive. The early (86 & 87) fan controllers had no overloading protection built in, so they can fail if the fan ever stops turning (or drags) for any reason. A stick in the blades for a brief moment is all it takes sometimes. 88 & later they added self-protection and could shut power down going to the fan motor, rather than smoke the output power transistor in the controller.

@vwmg,

Yeah... in the FSM the minimum specified temp for the cooling fan to kick on is 308 degrees fahrenheit. Most motor oils are already permanently junk by the time that fan kicks on.
 

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@PatrickB,

If you ever get a good fan control unit you can add a relay between it and the fan motor to help keep the new controller alive. The early (86 & 87) fan controllers had no overloading protection built in, so they can fail if the fan ever stops turning (or drags) for any reason. A stick in the blades for a brief moment is all it takes sometimes. 88 & later they added self-protection and could shut power down going to the fan motor, rather than smoke the output power transistor in the controller.

@vwmg,

Yeah... in the FSM the minimum specified temp for the cooling fan to kick on is 308 degrees fahrenheit. Most motor oils are already permanently junk by the time that fan kicks on.
I don't have my service manual sitting in front of me ?, but I don't think it's 308 deg's ?, a little over 200 something ?, i'll have to look it up when and if I remember ?!..lol.
 

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I just want to toss this in, and leave it be :). do I think a manual over ride switch to turn the fan on is a bad thing ?..NO !. what I do believe , is if the sensors and all is working like it was when it left the factory ?, then there is no reason to start adding all these after market parts on there just because no one wants to replace that 60 dollar ( give or take ) sensor to operate the oil temp sensor to get the fan to turn on, that's all I am trying to point out :). I have my '89 trx350D foreman complete stock except the tires ?, and a winch, and not once have I had a oil temp fan issue sense I starting riding it ?. to each their own :).
 

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I don't have my service manual sitting in front of me ?, but I don't think it's 308 deg's ?, a little over 200 something ?, i'll have to look it up when and if I remember ?!..lol.
Ya, I was wrong about the kick on temp. I don't know where I got the 308 figure from... but thanks for correcting me shadetree! The FSM states:

"When oil temperature goes over 110-130 C (270-306 F) sensed by the oil temperature sensor, the fan motor operates through the control unit.
When oil temperature goes over 170-190 C (378-414 F) the oil temperature indicator comes on through the control unit and alerts that the oil temperature is rising critically high"



I just want to toss this in, and leave it be :). do I think a manual over ride switch to turn the fan on is a bad thing ?..NO !. what I do believe , is if the sensors and all is working like it was when it left the factory ?, then there is no reason to start adding all these after market parts on there just because no one wants to replace that 60 dollar ( give or take ) sensor to operate the oil temp sensor to get the fan to turn on, that's all I am trying to point out :). I have my '89 trx350D foreman complete stock except the tires ?, and a winch, and not once have I had a oil temp fan issue sense I starting riding it ?. to each their own :).
I agree that we disagree. :) I believe that if the oil temp sensor and all is working as it was designed when it left the factory, that the factory engineers screwed up big time and never took the opportunity to correct their error in subsequent years.

Why? Because most (if not all) motor oils available in 1986 thru 1989 could not survive the minimum 270 degree temp required to kick the fan on. The spec ranges from 270 up to 306 degrees and is still considered normal by Honda! And yes, Honda branded oil was one of those incapable oils as well, that could not survive those extreme high temps. The same oil that was put in the crankcase when buyers took them home from their dealer was overheated and was completely junk when that cooling fan kicked on for the very first time.

I doubt if the Honda recommended motor oil sold today will survive those extreme temps either.

Only a very few expensive synthetics are likely to survive several heat saturation cycles over the 270 - 306 degrees range, for the life expectancy of an oil change. None of those high dollar synthetic oils are capable of surviving the 378-414 degrees temps required to kick on the warning light.

The point I'm making is that Honda screwed it all up bigger than Dallas. It may have been one of their biggest blunders ever. OEM parts can't ever fix it. So leaving it stock is not ever gonna be a safe option for anyone who puts their machine to work. Its gonna get fixed right this time.
 

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I don't have my service manual sitting in front of me ?, but I don't think it's 308 deg's ?, a little over 200 something ?, i'll have to look it up when and if I remember ?!..lol.
Ya, I was wrong about the kick on temp. I don't know where I got the 308 figure from... but thanks for correcting me shadetree! The FSM states:

"When oil temperature goes over 110-130 C (270-306 F) sensed by the oil temperature sensor, the fan motor operates through the control unit.
When oil temperature goes over 170-190 C (378-414 F) the oil temperature indicator comes on through the control unit and alerts that the oil temperature is rising critically high"



I just want to toss this in, and leave it be :). do I think a manual over ride switch to turn the fan on is a bad thing ?..NO !. what I do believe , is if the sensors and all is working like it was when it left the factory ?, then there is no reason to start adding all these after market parts on there just because no one wants to replace that 60 dollar ( give or take ) sensor to operate the oil temp sensor to get the fan to turn on, that's all I am trying to point out :). I have my '89 trx350D foreman complete stock except the tires ?, and a winch, and not once have I had a oil temp fan issue sense I starting riding it ?. to each their own :).
I agree that we disagree. :) I believe that if the oil temp sensor and all is working as it was designed when it left the factory, that the factory engineers screwed up big time and never took the opportunity to correct their error in subsequent years.

Why? Because most (if not all) motor oils available in 1986 thru 1989 could not survive the minimum 270 degree temp required to kick the fan on. The spec ranges from 270 up to 306 degrees and is still considered normal by Honda! And yes, Honda branded oil was one of those incapable oils as well, that could not survive those extreme high temps. The same oil that was put in the crankcase when buyers took them home from their dealer was overheated and was completely junk when that cooling fan kicked on for the very first time.

I doubt if the Honda recommended motor oil sold today will survive those extreme temps either.

Only a very few expensive synthetics are likely to survive several heat saturation cycles over the 270 - 306 degrees range, for the life expectancy of an oil change. None of those high dollar synthetic oils are capable of surviving the 378-414 degrees temps required to kick on the warning light.

The point I'm making is that Honda screwed it all up bigger than Dallas. It may have been one of their biggest blunders ever. OEM parts can't ever fix it. So leaving it stock is not ever gonna be a safe option for anyone who puts their machine to work. Its gonna get fixed right this time.
not sure what the temp is on Castrol 10w-40 ?, but that's what I run In all my atvs, no problems yet ?!. lol. I never buy Honda oil, not worth the price, when I can buy a good brand name oil for less :).
 

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My brother runs Castrol oil too. Seems to be doing fine in his 450 Foreman. I'm still on the fence deciding which oil to use this time. Need some hard data on it before I'll adopt it.
 
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