[shrade]

A while back I recall a member mentioning he installed a manual switch on his '05 400 AT. Would like to do the same on mine, seems to get pretty warm before the fan kicks on. would appreciate any help, tried a search or two came up with nothing.

 

[wheelsquad]

A while back I recall a member mentioning he installed a manual switch on his '05 400 AT. Would like to do the same on mine, seems to get pretty warm before the fan kicks on. would appreciate any help, tried a search or two came up with nothing.

Very well could have been me.

Here's a recent thread where @retro explains why you do NOT want to just ground the oil temp sensor wire: https://www.hondaatvforums.net/foru...0-2006-trx400fa-stator-keeps-burning-out.html

What I did on mine was just disconnect the quick connect that is right before the fan, and ran a power wire with toggle switch direct from the battery to the positive connection on the fan, and grounded the other one to chassis. I knew I had +/- right by the fan spinning the right way.

 

[retro]

You have several options for sure! You could put a 100k ohms potentiometer in parallel across the light blue wire and ground at the fan control unit and adjust for a lower oil temp fan kick on to keep the automatic fan feature in case you forget to turn on the manual fan switch. You could add a relay and a switch to over ride the auto fan feature as well. In that manner you'd have both auto and manual fan control + adjustable fan kick on temp while in auto mode. Or you could leave the trimpot out and wire in a relay and switch, or just bypass the fan control unit and wire in a manual switch as wheelsquad has done.

 

[shrade]

Thanks guys, need to decide which way to go.

 

[wheelsquad]

You have several options for sure! You could put a 100k ohms potentiometer in parallel across the light blue wire and ground at the fan control unit and adjust for a lower oil temp fan kick on to keep the automatic fan feature in case you forget to turn on the manual fan switch. You could add a relay and a switch to over ride the auto fan feature as well. In that manner you'd have both auto and manual fan control + adjustable fan kick on temp while in auto mode. Or you could leave the trimpot out and wire in a relay and switch, or just bypass the fan control unit and wire in a manual switch as wheelsquad has done.

I knew you had something figured for it that nobody else would. So I love the adjustable auto fan option. But what if the temp sensor goes out? Is there a way to have the fan always on in that case or some other way to indicate a sensor failure? Other than a secondary temp sensor with display?

 

[retro]

Yeah, we could monitor the voltage on the light blue wire going to the oil temp sensor and if/when that voltage goes high (meets or exceeds a predetermined threshold value), energize a relay to start the fan motor and/or alert the operator with a piezo buzzer and/or a warning light.

Oil temp sensors always fail by resistance going too high above their normal range due to oil overheating event(s). If they ever failed by resistance going too low out of their normal range (or shorted) the fan motor would start early... before the oil reached operating temp. So you would not need to be concerned about the sensor failing low, just catch it if it ever goes high and you're golden.

We know the sensor resistance is normal while it measures between 9.5k to 10.5k ohms @68 degrees (F)... thats all the info ya need to build whatever ya want on top of it.

Incidentally, if you have a sensor that is deteriorated to a point where it is out of range high, a 100k ohms trimpot connected in parallel with the sensor will allow ya to reel it back in and make it functional again, until the sensor can be replaced.

EDIT: This method would also kick on the fan/alert the operator if the oil temp sensor wire were unplugged, or if a stick pulled it loose from the sensor while riding.

 

[retro]

If you're interested in one them fan gizmos @wheelsquad lemme know. It would be simple and very inexpensive to build. There might be anywhere from 1-4 parts required... a zener diode, resistor, transistor and a relay should do it. But I'd probably get it down to just two or three parts after some testing... and after sleeping on it. It would probably cost more for weatherproof wire connectors and a tiny enclosure than it would cost for components. So maybe about $10 or so...?

Carrying it one step further and building a complete fan control unit (adjustable factory replacement unit) that included failsafe features could be done for a few bucks more using the same 2-4 parts to control the low side. Hollar when the snow is getting deep... I'll be looking for stuff to do.

 

[wheelsquad]

Yeah, we could monitor the voltage on the light blue wire going to the oil temp sensor and if/when that voltage goes high (meets or exceeds a predetermined threshold value), energize a relay to start the fan motor and/or alert the operator with a piezo buzzer and/or a warning light.

Oil temp sensors always fail by resistance going too high above their normal range due to oil overheating event(s). If they ever failed by resistance going too low out of their normal range (or shorted) the fan motor would start early... before the oil reached operating temp. So you would not need to be concerned about the sensor failing low, just catch it if it ever goes high and you're golden.

We know the sensor resistance is normal while it measures between 9.5k to 10.5k ohms @68 degrees (F)... thats all the info ya need to build whatever ya want on top of it.

Incidentally, if you have a sensor that is deteriorated to a point where it is out of range high, a 100k ohms trimpot connected in parallel with the sensor will allow ya to reel it back in and make it functional again, until the sensor can be replaced.

EDIT: This method would also kick on the fan/alert the operator if the oil temp sensor wire were unplugged, or if a stick pulled it loose from the sensor while riding.

If you're interested in one them fan gizmos @wheelsquad lemme know. It would be simple and very inexpensive to build. There might be anywhere from 1-4 parts required... a zener diode, resistor, transistor and a relay should do it. But I'd probably get it down to just two or three parts after some testing... and after sleeping on it. It would probably cost more for weatherproof wire connectors and a tiny enclosure than it would cost for components. So maybe about $10 or so...?

Carrying it one step further and building a complete fan control unit (adjustable factory replacement unit) that included failsafe features could be done for a few bucks more using the same 2-4 parts to control the low side. Hollar when the snow is getting deep... I'll be looking for stuff to do.

Geez, I need to finally get my act together and have someone be my hands and can coach them in putting a new oil temp sensor in finally so I can be ready for my own retro-gizmo.