Not sure anyone cares but I decided to take a crack at creating my own thermostat fan switch for a 1994 Polaris 300.
The thermostat fan switch part number 4110114 which I believe supersedes 4010211 is now obsolete. It is used on a lot of the older (late 80s and early 90s) air cooled ATVs. What I’ve found so far on the internet is that most folks just rewire the fan to a switch and turn it on as needed (under heavy load, idling, going very slow, etc.) As my wife and daughters will be riding this machine I thought it would be better to create a new thermostat switch.
What you need:
- Old Thermostat fan switch to use as a mount
- White Rodgers thermostat switch part number 3F11-225. this switch closes at 225 degrees F and opens at 195 degrees F. Also called Bimetal disc or snap switch. $9.41 plus shipping from Mouser electronics
- A custom made metal mount with three holes (simple)
- Various nuts, bolts, and washers
- Thermal compound paste like used for heat sinks on a computer CPU (not sure if this is necessary)
- Loctite
I took the old thermostat and broke off the black plastic part and tabs and then ground the brass part flat on a grinding wheel to create a mount.
Then I made a simple metal piece with three holes that would be used to mount a new White Rogers thermostat switch.
Add some thermal compound paste to the contact areas that will transfer heat to the switch. I don’t know if the air temp or frame temp is the driving factor to trip the switch so I used thermal compound just in case frame temperature is critical.
Assemble all the parts and mount on your ATV. Please note the following:
- I carefully bent the Thermostat switch tabs 90 degrees so they were similar to the original switch.
- Although it might not be effective because the bolts are too small, permanent Loctite was used on the nuts and bolts
- 2 washers were added to the to the mount to compensate for the bolt heads to ensure there would be good thermal contact to the mounting location.
I did some testing with an infrared laser thermometer and found that when the frame where the fan switch is mounted gets to ~260 degrees F enough heat is transferred to the switch so it closes at 225 degrees. When it cools off to 195 degrees F then the switch opens and turns off the fan.
If you want too have the fan turn on at a lower temperature you can use a different switch with a lower temperature trip point. There is a thermostat switch that closes at 180 degrees but I think the fan would be on more than needed.
Not really sure how durable this home made part will be but I can keep folks posted as we use the ATV.
Pics below and in next post.
Hope this is helpful to someone.
Pigseye
