I did a search and read thru several threads about this subject but still don't have a solution. I have an 03 700 twin sportsman and I can't get the fan to come on. I have replaced the thermostat and the temp sensor at the bottom of the radiator. The radiator is full and the coolant is circulating back into the tube under the cap. I have been running the quad with the front end jacked up to get air out. If I unplug the sensor and put in a jumper, the fan will run. I did a continuity check on the sensor and it is open. It seems to me the sensor is either bad or somehow not able to sense the coolant temp. It's a new sensor so I'm leaning towards it not being able to sense the coolant temp. If I let it run long enough, the speedo starts flashing and the little pic of a thermometer appears. Does anybody have any ideas on what I can do next?

 

Check under the panel, does show two 20 amp circuit breakers in sealed pouches. I just have the 2005 manual wiring schematic,but still shows one of the breakers is for the fan just like the parts breakdown on the 2003 shows. Could be the problem if shorted out. Just check that you have power on each side of the pouch,if not slice the pouch and check for corrosion,bad connection. See if this helps. Plus you can look here under "electrical" on your model and see. Browse OPT

 

I'll do that, thanks. If I didn't have power coming out of that breaker, why would the fan run when I bypass the sensor. It looks like the sensor is after the pouches so there should be power coming out of the sealed pouch, right? I may not be able to get to it until Sunday night but I'll check this thread for answers about the power. I've got 12.27v to ground going to the sensor but nothing coming out.

 

Yes, power should be coming from the sealed circuit breaker at all times on either wire side. Don't know if this is the problem,but also make sure you also check all the connectors. Sounds like that may be the problem if you bypass the sensor connector and the fan comes on? The sensor completes the circuit when hot and triggers the fan motor. OPT

 

Yeah, I did a continuity check on the sensor and it's open so the circuit is not complete. Everything is telling me the sensor is either bad or not getting hot enough to close the circuit.

 

You can always use a heat gun if you have one or a good hair dryer right at the sensor itself (or even drop it in hot water) and see if the resistance changes from the cold state. If so then the sensor wouldn't be the problem. OPT

 

That will probably be my next step I guess. I'll pull the sensor and put it in hot water and check continuity. Thanks for your help and I'll come back later with my results.

 

I tested the sensor in boiling water and it works fine. I plugged it in while it was hot and the fan came on. Next I refilled the system and bled out the air by running it with the cap off and the front end jacked up in the air. The fan will now run like it's suppose to. BUT....it looks like I may have a leak in the radiator. At first I thought the dripping was just from me spilling coolant when filling the system but it didn't stop. The higher the water temp got, the worse it leaked. Then the fan would come on and the leak would slow down. When the engine is shut off and cooled down, it doesn't leak at all. Does that Stop Leak stuff work? Or should I just pull the radiator and get it repaired? I looked up a price on a new radiator and it was like $450 so I'd rather not buy a new one.

 

Don't trust Stop Leak! Plus you don't want that stuff circulating through the system. Pull the radiator and see if a radiator shop can possibly solder the leaky coolant fin. If they can't at least you've tried. OPT

 

Thanks......I've never tried that Stop Leak stuff before. I'll pull the radiator and see if I can get it fixed. Is it all aluminum? If it's got copper lines with aluminum fins I can fix it but if the lines are aluminum I don't want to even try. I've tried soldering aluminum before and it isn't pretty.....lol. Copper no problem.