fan not operating - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

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post #1 of 31 Old 05-19-2020, 01:12 AM Thread Starter
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fan not operating

1994 Klr 30000 miles I installed the thermo-bob and my fan doesn't turn on. The fan runs when I touch the wire to the engine fin. It warms up to about 1/2 way on the gauge and the fan doesn't turn on. Am I being to impatient. I can say not sure the fan was working before I installed the thermo-bob part of why I probably thought I needed it. I uninstall the thermostat and tested it and it opens properly I did buy a new switch and installed it also. Not sure how to proceed. Any ideas. I'm not much of a mechanic but this seemed pretty simple. Thanks in advance
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post #2 of 31 Old 05-19-2020, 05:49 AM
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Procedure for testing thermal switch in service manual (your wife WILL let you use here kitchen range, right?).

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post #3 of 31 Old 05-19-2020, 07:20 AM
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It is not supposed to turn on until the needle hits the red mark on the gauge.
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post #4 of 31 Old 05-19-2020, 09:19 AM
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Quote:
Originally Posted by Tom Schmitz View Post
It is not supposed to turn on until the needle hits the red mark on the gauge.
True! If the temperature gauge needle stays out of the far-right red zone (Generation 1, anyway), you don't need to activate no stinkin' radiator fan!

On Generation 1s, an operational thermal switch in the lower radiator closes at a coolant temperature in that region of around 200 degrees F. (if I remember correctly). This closure of the thermal switch contacts connects a hot wire from the fan relay to ground, closing the relay's contacts and sending power to the fan motor. Don't think Generation 2s have fan relays; instead, direct full fan motor power is routed to the thermal switch. (No speaka much Generation 2; corrections welcomed!)

For those using temperature gauge degree overlays: The temperature gauge measures coolant temperature near the cylinder head, typically higher than coolant temperature at the bottom of the radiator.

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post #5 of 31 Old 05-19-2020, 10:23 AM
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What Tom said; sounds like everything is operating as designed.


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post #6 of 31 Old 05-19-2020, 10:50 AM
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Quote:
Originally Posted by Tom Schmitz View Post
It is not supposed to turn on until the needle hits the red mark on the gauge.
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Originally Posted by DPelletier View Post
What Tom said; sounds like everything is operating as designed.


Dave
Well it is not very often that I disagree with either Tom or Dave to much degree, but I will on this.

IME, most KLR fan switches will turn on by at least 3/4 of scale, my Gen 1 turns on at 5/8 scale. And as long as it stays below the RED Zone, all is well.

With the Thermo-Bob installed my Gen 1 the gauge normally hovers between 7/16 & 9/16 of temp scale on the open road & the fan is NOT running. Just as it is supposed to operate.

To the OP,
I think that you were overly impatient.
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post #7 of 31 Old 05-19-2020, 11:50 AM
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Paul,

Instead of being lazy and just agreeing with Tom, I should have said that half way on the gauge doesn't turn on the fan on either of my KLR's and that the fan not coming on at 1/2 way is normal. He's tested the fan switch and everything seems to be functioning as I would expect. I suspect he's chasing a non-existant problem. Better?

Dave
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post #8 of 31 Old 05-19-2020, 01:18 PM Thread Starter
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Thanks everybody I have never paid any attention to when it comes on. Thought i might be being a little in patient. Since everything else seemed correct. Had this bike quite a while and tires and oil about all ever done ( yes have the doo and a thermobob) and what started this whole mes was breaking the subframe in march. Thanks again
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post #9 of 31 Old 05-23-2020, 10:13 AM
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Quote:
Originally Posted by pdwestman View Post
Well it is not very often that I disagree with either Tom or Dave to much degree, but I will on this.

IME, most KLR fan switches will turn on by at least 3/4 of scale, my Gen 1 turns on at 5/8 scale. And as long as it stays below the RED Zone, all is well.

With the Thermo-Bob installed my Gen 1 the gauge normally hovers between 7/16 & 9/16 of temp scale on the open road & the fan is NOT running. Just as it is supposed to operate.

To the OP,
I think that you were overly impatient.
Indeed, the radiator fan on my Gen II sans T-bob activates at about 3/4 of the temperature scale, well ahead of the needle aligning with the red area.

Jason
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post #10 of 31 Old 05-23-2020, 04:47 PM
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Gauge, no 2 indicate the same I have found.

I particularly liked my Ducati 851S temp gauge. About the time it dropped a cylinder to help with cooling, the temp needle would be almost in the red. On the 916 the fans kicked in when the gauge was almost 1/2 way and were as loud as the dry clutch!!!!
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