Buddy's TE 250 fan constantly on

My buudys 2010 te 250 fan comes in with ignition switch and stays on constant. Temp sensor? What do y guys think? Thx again!!!

hmmmm- looks like the 2010 TE310 & TE250 have different manuals.... and of course, I can't read the wiring diagram of the 250 easily. But it looks close to the 310 so let me throw a few suggested places to look at.

[later edit: Actually, a quick & dirty sensor test may be to just unplug it- if the fan stops (cold bike, key on, engine off?) then the sensor is bad. <--- yeah, do that first, that'll tell you fast.]

1st, try pulling the orange wire w/ a green stripe off of the fan relay (this may involve a lot of hand-waving if it is bundled in a multi-wire connector, as is likely). If the fan continues to run, it's probably a bad relay. (option 1 test: unplug the relay and test the 2 main terminals: open circuit means it's probably good; option 2 test- else just plug in another relay and try that one). This tells you it's the relay that is bad.

If the relay passes the above test, we have more of a mystery: put your money on a bad temperature sensor (hopefully, it's not a bad ECU). It's denoted as a WTS (water temperature switch) or #33 "coolant temperature sensor" on the wiring diagram. I'm guessing it is supposed to be at infinite ohms (ie, open) when the water is cold; you may find it closed (50ohms or way less) at any temperature- meaning it's bad. Just buy it and cross your fingers.


Try these two test and let us know what you find. BTW, my TE310 has been running fine, with the fan removed, in 90° F temps; although that's close to my personal riding limit- even while wearing an evaporative vest.

good luck.

Change tempsensor and it will work again.

My TE250 never had the fan come on.

I removed it.

I wanna do some major backpedaling here: on newer 250/310s there are two coolant temp sensors. The one that controls the fan is a simple (bimetallic I'm guessing) switch that is in the coolant line to the right radiator. It is normally open, and when it reaches its trip point (200-212°F) it closes and the fan comes on... no ECU is involved (well, 'cept for turning on the dc relay that gives power to all the extraneous stuff after startup). It's called the Thremo-switch; and I don't think it's in the wiring diagram. Older 250/310s don't appear to have this fan switch.

The other sensor is the same in your friend's bike, Jimmy: it tells the ECU the water temperature. The ECU on his bike adjusts the map (not really- it goes to a different dimension in the table) for things like FI timing/duration and possibly ignition timing... and in your buddy's case: turning the fan on/off. It is sometimes called the coolant temperature sensor (CTS) or water temperature sensor (WTS)

So- the fan being on all the time may be a symptom of the real problem. If it's NOT a bad relay, it's a symptom of a bad temp sensor, which can easily be replaced ($23 IIRC) or (god forbid) a bad ECU. But he shouldn't just toss the fan and continue on- because the ECU is dependent on this info that the sensor provides.

My sensor test above probably is not correct for your buddy's bike. Sorry about that.

Rich Mine never comes on either! lol

I agree Has is grabing a sensor from our dealer, I told him the same its cheap and takes 3 min to change so lets do it! Thanks for the reply Keep ya posted!

Yes, and it is tight riding up there!

My TXC310 fan runs all the time in tight stuff.

The fan on my 2011 TE250 never comes on... I guess I better look in to the temp Sensor. JonXX, lets talk! See you at BMP soon.

Ok so u just changed the temp sensor and fan still comes on with ignition switch. Is there another relay?

Hi Jimmy-
If I understand you right (?) you put in a new temp sensor, which didn't change a thing?

did you test the relay, which is a separate item (one of the 1" cube thingys usually near the airbox)? hell, swap a known good one in and try it.

Also, do you or your buddy have the manual?

I have the whole manual. and yes I changed the Temp Sensor, I will look for that relay Thank You

Did he buy his bike new? If not, is it possible the previous owner hard-wired it that way?

here's a simple test for you: unplug the wires from the fan relay and plug them into the light relay (or move the light relay over... whichever is easier for you). page 309, M.11 fan relay is #12; light relay is #13 on a stock bike with unmodified wiring.

turn the key on. fan off? good! ---> start the bike up (remember the lights won't work) & ride it until the fan comes on. fan comes on? good! ---> spend $2.95-9.95 on a new relay.

else any "no" answers means we got other problems.

try it and give us the results.

btw the wiring schematic on page 304, M.6 the fan relay is number 29 (it's NOT the solenoid... Manual is wrong)

Thanks Shovelhead! Thats a good idea! Andrew I was wondering the same thing!

I agree that is the case with mine!

I just switched my rad hoses out to eliminate the thermostat. It looks like my fan switch was also toasted. Since I was planning on traveling to ride today, I wired in a switch to turn it on or off.

Worked like a charm!

Thats a good Idea, how did you do it?