overheat light, what gives - K-Bikes.com - Excellence in Motion
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post #1 of 5 (permalink) Old Apr 1st, 2011, 1:20 am Thread Starter
Join Date: Mar 2011
Location: Amsterdam, , Netherlands
Posts: 6
overheat light, what gives

hi all,
first post so a short intro. hailing from the Netherlands on a '94 K75 RT with 136K Km (85K miles).
I've owned it for about 9 happy months and 5K Km (can't ride much during frozen roads season, says the scrape I wisely put on the fairing to remind me...).

all in all the bike is great! I'm looking forward to some touring around, so far I only had time to skip over to Belgium and ride around in Holland.

it does have one hickup that stands between us and bliss though, and I was hoping maybe someone here could give a helpful tip.
(I've read many a post and article, but never with this specific conjunction of symptoms, at least to my layman's understanding)

in short, the dangin' temp light comes on...

- after about 20-30 minutes of riding it will start glowing.
- light reacts to riding faster / lower RPM
- fan doesn't come on (!) although I'm almost sure it did at least once before, and I'm sure it did once after this problem started
- after riding with heat lamp on, lamp will typically also burn from the get go on first few Km's of the next ride, even a day later when started stone cold
- I think it first happened around November after riding through a deep puddle in the road where water splashed all over the bike and myself, dunno if this is related though.
- I don't think it's actually overheating, but have no clue how to check this.
- almost certainly unrelated, but who knows: when my left grip heating failed due to corrosion in the thin wire heating element inside the handle,
I peeled off the insulation and replaced about half an inch with normal wire to close the circuit which solved the problem

what have I checked/done:
- splashed some contact spray on the fan's connector
- verified fan IS operational when tested by jumper in the relay box
- checked temp probe resistance when cold, 3.3K Ohm
- checked coolant level in reservoir
- gone crazy already (didn't help)

any good leads on what to check / do next to localize this problem??


edit: after writing this post I let it idle on the center stand again, this time I gathered courage and waited 25 minutes - the fan came on, and no temp light!
you know how you go to the mechanic and the problem solves itself?
here's fingers crossed that it's all good just because I finally asked for help..
or maybe taking the relay out and reinserting it fixed a loose connection somewhere..?
I'll take him out for a spin later and see if he doesn't "overheat" again.
any thoughts are obviously still very welcome.

Last edited by dave-hyman; Apr 1st, 2011 at 5:19 am.
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post #2 of 5 (permalink) Old Apr 1st, 2011, 7:18 am
PsyKotic Waterfowl
Join Date: Aug 2006
Location: Seattle, WA,
Posts: 1,328
1) Follow the wire from the temp sensor and see if it's insulation has worn off somewhere and is grounding.

2) Your temp relay (the white one) may need replacing.
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post #3 of 5 (permalink) Old Apr 1st, 2011, 12:43 pm
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Location: Burton, British Columbia, Canada
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You may want to have a good look at/through the radiator , you should see how much crap, dead bugs,tar and little rocks I have pulled out of some of them and how many fins I have straightened over the years. I screen everything now.....much better!

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
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post #4 of 5 (permalink) Old Apr 2nd, 2011, 2:12 am Thread Starter
Join Date: Mar 2011
Location: Amsterdam, , Netherlands
Posts: 6
thanks FlyingDuck and H96669.

the relay or hopefully one of its connection points do sound like the most likely culprit, still investigating.
the radiator has a protective grill/screen in front of it and looks OK from here, but next time I have the fairing off cleaning it will surely get done too. (thanks for the tip)
if fidgeting with the relay didn't solve the problem, I'll try replacing it.
I see them offered used for 10 - 17.50 euro, not as bad as I thought if it comes to that.

happy riding one and all,

'94 K75 RT
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post #5 of 5 (permalink) Old Nov 13th, 2011, 12:09 am Thread Starter
Join Date: Mar 2011
Location: Amsterdam, , Netherlands
Posts: 6
Thumbs up

hi everyone,
I want to write a quick thanks and follow up for future reference.

Originally Posted by FlyingDuck
1) Follow the wire from the temp sensor and see if it's insulation has worn off somewhere and is grounding.

2) Your temp relay (the white one) may need replacing.
while changing tires yesterday, I replaced the switch (white relay box under the tank) after 7 months riding with an always on overheat light .
problem solved for 20 euro ($28 or so).

Flying Duck, you hit it on the head. thanks, mate!
and thanks k-bikes forum!

'94 K75 RT
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