Coolant Temp. Indicator - Honda TRX Forums: Honda TRX 450R Forum
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  • 1 Post By duke416ex
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post #1 of 5 (permalink) Old 05-18-2017, 07:40 PM Thread Starter
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Coolant Temp. Indicator

Purchased an 07 450er last week. The previous owner had a toggle switch hooked up to the electric fan. I was hoping to reverse this and put it back the way it was but there was a wire cut preventing me from doing so. The red temp. indicator light on the dash isn't working at all. The wiring coming off the indicator light and the wire coming from the temperature sensor on the motor are both intact and connected to the ICM. There is a black wire coming out of the wiring harness that use to go to the blue plug that the fan motor plug goes into. That black wire was cut off flush on the female side of that blue plastic plug and the other end cut off at the wiring harness.

That blue plastic plug where the fan plugs into, is some kind of voltage reducing plug (not sure what the technical name is) the wires going into the bottom off the fan motor are larger gauge than the wires coming out the top so I cant directly splice them together.

If the temperature sensor is bad, will the red indicator light work at all? It supposed to come on for a few seconds when turning the key on, correct? I would still like to have the red light working even if the fan is wired to a switch.

Last edited by Equalizer; 05-18-2017 at 07:42 PM.
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post #2 of 5 (permalink) Old 05-18-2017, 08:21 PM
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You need to hook up the yellow/blue wire from the 8 pin connector to the thermistor of the engine, at room temp you should read about 500 ish ohms at 24 Celcius from the pin to the block, the fan is driven by the CDI unit
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post #3 of 5 (permalink) Old 05-19-2017, 06:39 AM Thread Starter
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Thermistor? Are you referring to the Engine Coolant Temperature Sensor (ECT)? The blue/yellow wire from that is currently still connected to the ICM (Ignition Control Module). The names I'm using is what there called on the wiring diagram in the service manual.

The fan motor is currently disconnected because the plug has been cut off.

It looks like I'm gonna have to stick with having the fan connected to a toggle switch. I just want the red temperature light to work like its suppose to.
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post #4 of 5 (permalink) Old 11-02-2019, 12:00 AM
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I know this is an old thread but my temp light isn't working either, I have it connected directly and the fan runs fine constant, but the light never comes on. If someone has found a solution please let me know, thanks in advance.
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post #5 of 5 (permalink) Old 11-05-2019, 12:55 PM
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So you have your fan wired direct but not wired up to the temp sensor? Have you checked the bulb? If I am remembering correctly if the wire is just shorted out to run constant then the light would be on all the time so the bulb may be blown or may be unhooked. If it is shorted out then the cdi will think it is overheated all the time anyway and the light would basically tell you nothing.
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