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Gortex

Cooling fan question

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I have a 2005 Rancher TRX350FE ES.  I have been riding it in some pretty blistering Texas drought heat since I got it several weeks ago.  I have yet to hear/see the cooling fan come on as I have been riding.  A buddy has a newer 2x4 Rancher 420 and his comes on pretty quick after we start riding.  My fan works, I grounded the thermal oil sensor cable while the ignition switch was on and it came on every time.  I have read in places that it is not that uncommon for this year model and previous year models not to come on and some previous years didn't even have fans.  Also have read that typically the liquid cooled fans come on sooner and more often than these year models.  Anyone have any good insight?  Should I be concerned and is there something else I should check to see if system is working properly?

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Posted (edited)

best thing to do is check the resistance on your oil temp sensor and buy a new OEM sensor. 


The service manual has some information on the Oil Cooling System. You ought the run through the diagnostics so you understand a bit on it—I’m not familiar with the systems on the model. 

 

typically there’s a fan control unit working with an oil temp sensor. First step in diagnostics: When you switch on, the neutral light comes on steady and the oil light comes on momentarily and then goes out. 
 

The oil temp sensor uses a thermistor designed to reduce FCU circuit resistance as the oil gets hotter. At 77F (ambient air temp) Starts out about 10.5KOhms; then about 100C/212F it should be down to 1KOhm—fan comes on but oil (overheat) light stays off. At about 345F the sensor resistance should be less than 300 Ohm. That’s down 97% from the starting point! oil is hot enough to fry chicken. Fan should already be running but the warning light comes on.

 

As it ages, the oil temp sensor degrades and the resistance is slow to degrade. So you might be running at engine temp of 245F, your engine could be running hot, but your fan’s not kicking in. you can try testing temp sensor response by measuring resistance in hot oil at 100C. Have to take it out to do that. So that’s why I suggest buying a new sensor—don’t throw away the old one
 

Or, you’re also light on the throttle, good fuel/air mix, machine in good shape and just not getting as hot as your friend’s quad. 

D9E3EF19-FB05-47C5-B3B9-BEE0FE0704CB.jpeg

Edited by Goober

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Hi , toggle switch on , toggle switch off 

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Thanks for the info Goober and the picture of the process.  I am new to this and to ATV's in general, this is my first one, so I will play with it this weekend.  I am probably light on the throttle than most being a newbie, HAHA.

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Fishfiles,  I am considering that option as I have heard several say that is what they have done.  Just hate not knowing why something isn't working as it was designed, but I may have to get over it and go that route.  Thanks for the response.

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Air cooled fans take a LOOOONGGG time to come on vs the liquid cooled machines.

 

I've never had an aircooled machine overheat, whereas the liquid cooled machines we constantly have to pull over and wait on them to cool off if we're in the mud and their radiators get muddy.

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1 hour ago, Gortex said:

Fishfiles,  I am considering that option as I have heard several say that is what they have done.  Just hate not knowing why something isn't working as it was designed, but I may have to get over it and go that route.  Thanks for the response.

 

Davie White makes a fan controller , I got mine off Summit Racing , cost is less than 1/2 of what a OEM fan controller module alone sells for , if you can even get controller  for your 350 , I know 450s are no longer available and they cost $205 before they went no longer available , and you don't need any of the OEM wiring harness to make it work  ---the Davie White gives you digital temperature radding and is programmable  but it is not waterproof , so it is best to mount it in a water proof box 

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The Davie White uses a thru the fin of the cooler  thermocouple , which is good for me as this 300 , which never had a fan to start with , and it runs two fans and one is relocated  , the top section lights up red led and displays the temperature , the one in this pic does two fans and can be set separate temperatures , they make a single fan setup also 

 

 

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Jeepwm69, that seems to be the general consensus, 1) these take forever to come on and have to be super hot, 2) many didn't even come with fans and never burned up so I may be fine, because I don't push it too hard.  Thanks for the information and pics Fishfiles, I may look into that!

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