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radiator fan

2959 Views 15 Replies 7 Participants Last post by  Honda_KiLlEr660R
i was told the radiator fan is sopposed it kick on at 210 degrees and i rarley ever hear it come on so i bought a inline temp guage and i was at the local drags and ran bout ten times in a row and the temp said 240 and the fan was not on? it was 35 degrees outside but i think it should have come on. what is my problem. can i put it on a switch or is that not good?
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Fan diagnostics.............

Reach up behind the radiator, does the fan turn freely?

Remove the front plastic and gas tank. Right front corner of the tank is the thermostat housing and temp switch that controls the fan.

There is a red/white wire feeding the thermal switch, test it for 12 volts. Ignition and kill switch on. Yes?

A blue wire leaves the switch and goes to the fan.

Unplug the thermal switch and jump the two wires in the plug, the fan should run. Yes?

A blue and a black wire plug in to the fan, the blue can beconnected to the plus terminal of the battery and the black to negative or a frame ground. Fan should run.

Drain the coolant, remove the thermal sensor from it's housing, attach wires to the connections on the switch. Take the switch into the kitchen and put it in a pan of water. Hang it or support it from touching the bottom of the pan, you want the heat to transfer thru the water not the metal. Connect a Volt meter to the leads and set it for resistance. Put a meat thermomiter (sp) in the water and turn the burner.
The switch should read high resistance or open circuit below 210 deg, around 210 deg it should close and themeter should read low or no resistance. Turn the burner off and watch the drop in temperature the switch should reopen around 200 degrees.

While every thing is apart the thermostat is right there also, you can put it in the pan also and watch it open and close. 160 degree's is the point it should open.

Some people like to have a manual switch to control the fan. I you want one use the red/white and the blue, the two wires at the thermal switch. Place the manual switch in parallel with the thermal switch and you'll have both manual control and (if it works) the automatic switch. Just cut into the red/white and run a lead to one switch terminal and the other sie of the switch connect to the blue.

Well that got a little longer than I thought it would, hope it helps.
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i'm no electrician and i understood maybe the first quarter of that... Maybe some pics and few non-electrician words would be great.
cutters, pan, thermal switch, water, boil, wait till 210 degrees, drink a six pack,...voila..its done! :lol: :lol:
DECEPTiON21 said:
i'm no electrician and i understood maybe the first quarter of that... Maybe some pics and few non-electrician words would be great.
Must I?
That was too much typing the first time around. If you pick out particular words to redefine or parts of the process it I'll do what I can.
Nah, I'll tough it out...
the problem is usually a faulty temp sensor in the radiator. The temp sensor is located in the bottom left corner or the radiator. Remove the electrical plug from the back of the sensor, turn the key on, short the 2 pins in the female end of the electrical connector together, if the fan comes on its probably the sensor.

To test the sensor, pull it out and put it in some water, put heat to the water, put a thermometer in the water, when the water reached 210 +/- 6 degrees put a multimeter between the electrical leads of the sensor, if it is open but then goes closed after the temp comes up it fine.
DECEPTiON21 said:
Nah, I'll tough it out...
You sure?

Didn't mean to make it sound like it's an inconvienience. But I'd need to know what needs clarifying. CSR's method is a bit more consise.
yeah. i'll get it... i might learn something along the way
I think i got it... I did what CSR said and when i jumped the two pins in the female plug, the fan ran. Should i replace the sensor or just put it on a switch...?
I'd replace the sensor, that way you don't forget to turn it on. The switch is an option if you like but I wouldn't trust myself or others that may ride it to turn it on.
i am going to do both... Do i need to drain the coolant before i replace the sensor at the bottom of the radiator?

Just kidding, you can drain it first but you will still need to put a pan under to catch the remaining coolant that will pour out when you take the sensor out :thumbsup:
check all the electronics especially if you trail ride, could be some dirt or a little moisture up in there
a buddy of mine had the same problem a while back but it was just a little moisture that dried out
or just install a manual switch
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