radiator fan won't shut off

[pajyee]

Just changed my radiator out. As I was hooking everything back together-- my radiator fan turned on and won't seem to shut off. Anyone have any ideas about what the problem is?

[wanchesenative]

The temp sensor switch at the bottom of the radiator might be malfunctioning, but my first guess would be that a wire is contacting the frame and completing the ground circuit. The way the "switch" works is when the coolant heats up the switch, it "opens" to complete the ground in the circuit which turns the fan on. Check all the wiring and see if you might have a wire mistakenly connected to the frame causing a ground.

[pajyee]

Thanks for your help. I appreciate it. I took off the temp sensor switch from the old radiator and put it on this "new" used radiator and even replaced the wire connector (which broke in connecting and disconnecting)-- so it should be working properly, I'm thinking. Sounds like the issue might be at the ground wire at the mounting bolt. If I connect the mounting bolt, and the ground wire at the mounting bolt, doesn't the ground wire touch the mounting bolt which touches the radiator which touches the bike frame?

[wanchesenative]

The radiator should be grounded to the frame. I think this is what you are asking. The wire that plugs into the sensor should NOT be grounded to the frame. This would make a permanent ground. It is possible that the sensor is stuck in the "on" position causing a permanent ground, or maybe the new connector also touches the radiator. This would cause a permanent ground as well.

[pajyee]

If the sensor is stuck on the "on" position-- how do you make it unstuck? Or does that mean that I need a new sensor?

[wanchesenative]

I'm not real sure on the inner workings/repair of the sensor. I think it means a new sensor is in your future. Either that or do like many of us including myself and put a manual switch in it's place. Run the single wire going to the sensor to a simple toggle switch and then from the toggle switch to the frame for grounding. Then don't forget to cut it on and off as you start and finish your ride. I ran my battery down several times till I got in the habit. Now, it's just another part of my warm-up and shut-down.

[pajyee]

Thanks a lot-- appreciate your help! Can probably take it from here. Else, will return with more questions. Actually, let me ask a curiosity question. Why do so many put a manual fan switch on. Are the sensors unpredictable across the board? Are the thermostats not kicking on the fans fast enough? I do have a fear that I will leave it on. I've left the key in the ignition a couple of times already in the on position-- it will just be one more thing to remember.

One good thing to report is that with the change to a good radiator now (that is not gunked up with Bars Leak stuff and even with the fan disconnected)-- I was able to get to work and the temp gauge only got as high as half way (used to go to 3/4 way). It's not yet warm here in Northwest WA and I'm only going about 15 minutes-- but it is a step forward for me!

[wanchesenative]

Happy to help

[pajyee]

Wow-- you're fast. Modified the above post a bit.

[Jet⚡Black]

I'm not sure what happens on an electronic ignition bike when you leave the key on; as I have never done that. I have done it with a bike with a points ignition and yeah that's a bad one; it can fry your coil(s) in under 15 minutes.

[wanchesenative]

If you decide to go the way of a toggle switch, the po of my bike just drilled a hole in the instument panel and installed a switch there. I had to rewire it as I didn't like his job of it, but the location is very handy and easy to keep up with while riding in case I forget.

[pajyee]

So, out of curiosity-- why do so many choose to install a manual switch? Is the system notorious for failing?

Would you happen to have a picture of what your switch and wiring looks like? Would like to learn from your good decisions.

[wanchesenative]

I don't but I will see if I can get some today. As far as the reasoning for adding a switch, I think it is just an economy thing. From what I remember, a new switch is fairly expensive for what it is and a toggle switch is cheap.

[pajyee]

That would be awesome if you could get some pictures up. Thanks for all the info.

[wanchesenative]

Here is a picture of where my switch is mounted. The previous owner drilled a hole in the "dash" I am assuming from the backside so as not to hit anything vital. As far as hooking it up, all you have to do is extend the wire that is currently connected to the sensor so that it will reach wherever you mount the toggle. From there, just run the other side to a ground on the frame.

[pajyee]

That looks like a good place for it right next to the key. Thanks for the pic. Another question I had is-- since my sensor is stuck on the "on" position-- will switch still work?-- or doesn't that matter?

[wanchesenative]

The "sensor" is just an automatic switch controlled by the water temp in the radiator. When you remove the wire from the sensor and attach it to the toggle switch, the sensor just becomes essentially a plug for the hole in the radiator. It doesn't matter what it is doing except plugging the hole.

[Jet⚡Black]

That's a nice place for the switch; seems hard to forget that close to the key