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Discussion Starter #1
hi im working on a trx500fa6 (2006} my cooling fan is good, but doesn't work, ive traced the wire from the sensor in the lower front and grounded it and the fan is still missing the ground side leg at the fan,im thinking the 3 plug in module/ brain up in the front . ?? any tips or ideas please id love to know,
 

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most cooling fans only have two wires one is power, other is ground. green is ground !.
 

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Discussion Starter #3
Yes sir, ive got my 12v im missing the ground signal. im thinking it goes through the module after getting signal from the temp sensor. ive tested the wires for breaks etc. and grounded the wire at the sensor..The fan runs great when a ground is applied to it. im trying to understand how that circuit works and if im right in thinking its that module. also it seems to have a thermos coupling mounted on the left side under a small black cover which tested ok .
 

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You're on the right track... the fan control unit monitors the oil temp via voltage drop through the oil temp sensor. The control unit kicks the fan on by supplying negative ground to the fan motor. The battery voltage positive fan motor lead is fused in the fusebox. There are diagnostic steps outlined in the service manual for the cooling system which you'll need to follow, to be sure which part needs replaced.
 

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Discussion Starter #7
sorry for not getting back sooner , ive been catching up on other jobs, now back to the trx500fa , I have ran the test per manual,, as stated when I ground at the etc sensor the fan runs, I replaced that sensor as the manual keeps pointing to it , nothing has changed , I also disconnected the plugs ran test etc.. as it read in the manual . still missing my ground signal to the fan , im really thinking the ecm main board, which im afraid to price lol . even when grounding the oil temp sensor nothing, but when grounding the coolant sensor it runs.
 

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Try unplugging and measuring the resistance of the oil temp sensor at room temp. It should measure between 9.5 k ohms to 10.5k ohms at approximately 68 degrees F.

It sounds like the coolant temp sensor is working right.
 
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