K100 Cooling Fan requires Brain/How get one?? - K-Bikes.com - Excellence in Motion
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post #1 of 16 (permalink) Old Jun 27th, 2008, 11:10 pm Thread Starter
 
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K100 Cooling Fan requires Brain/How get one??

Any thoughts about where to find a replacement for the Motronic brain for my 91 K100?

I believe the bad brain is how come my fan won't come on when driving s;lowly in town in the hot summertime.

Having a tough time locating a used one.

I hear new ones when locatable cost a thousand bucks!!

I am going to bed now (Friday evening, @2300) here in Dallas, to dream of a used Motronic brain appearing out of the blue!! Alternate realities about sources very very welcome.

Thanks,

Jacques Vroom
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post #2 of 16 (permalink) Old Jun 28th, 2008, 10:33 am
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Quote:
Originally Posted by jacquesvroom
Any thoughts about where to find a replacement for the Motronic brain for my 91 K100?

I believe the bad brain is how come my fan won't come on when driving s;lowly in town in the hot summertime.



Thanks,

Jacques Vroom
How did you come to that conclusion??
Please read the attachment before you tear things apart.
Attached Files
File Type: pdf cooling fan & temp. sensor.pdf (462.7 KB, 86 views)

Bruce C
'04 K1200RS Capri Blue(totaled)
2008 Triumph Sprint ST

Last edited by brucecha; Jun 28th, 2008 at 2:19 pm.
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post #3 of 16 (permalink) Old Jun 28th, 2008, 8:31 pm Thread Starter
 
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Bruce, Thanks for your helpfulness...

but that separate temperature sensor is only present in older K's—or at least definitely not present in my case!

What passes for logic is this:

a. Bike overheats in slow traffic, especially quickly at stop lights.
b. When you look inside radiator/fan assembly, you notice fan never rotates, no matter how hot engine gets.
c. Disassembly shows fan-motor clearly like buffalo bill—defunct. Plastic stuff melted into brushes, etc. All very ugly and fully permanent-looking in its defunctness.
d. Associated relay also gives very powerful visual indications of similar defunctness.
e. Obtain "new" fan motor and relay. Both work fine separately and together, but not back on the bike.
f. "Feels" like motronic brain also defunct in the area of temperature-sensing-communication. "

"What else could it be???", as we sometimes say here in Texas...

Thanks again for your thought.

Jack Vroom
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post #4 of 16 (permalink) Old Jun 28th, 2008, 10:41 pm
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Try "Beemer Boneyard" for another Motronic.

Bruce C
'04 K1200RS Capri Blue(totaled)
2008 Triumph Sprint ST
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post #5 of 16 (permalink) Old Jun 29th, 2008, 2:01 am Thread Starter
 
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Thanks. I did.

But they don't have any. Recently sold last one they had! Maybe they will eventually get another, but my fantasy was that I could find another one somewhere else right away...

Thanks again.
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post #6 of 16 (permalink) Old Jun 29th, 2008, 11:16 am
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Quote:
Originally Posted by jacquesvroom
but that separate temperature sensor is only present in older K's—or at least definitely not present in my case!

What passes for logic is this:

a. Bike overheats in slow traffic, especially quickly at stop lights.
b. When you look inside radiator/fan assembly, you notice fan never rotates, no matter how hot engine gets.
c. Disassembly shows fan-motor clearly like buffalo bill—defunct. Plastic stuff melted into brushes, etc. All very ugly and fully permanent-looking in its defunctness.
d. Associated relay also gives very powerful visual indications of similar defunctness.
e. Obtain "new" fan motor and relay. Both work fine separately and together, but not back on the bike.
f. "Feels" like motronic brain also defunct in the area of temperature-sensing-communication. "

"What else could it be???", as we sometimes say here in Texas...

Thanks again for your thought.

Jack Vroom
You might want to check on www.webparts.com parts fiche and look for the sensors that you say are not on your '91 K100. I found a water temp. sensor under engine/lubrication system/ cooling system-water hoses.

Bruce C
'04 K1200RS Capri Blue(totaled)
2008 Triumph Sprint ST
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post #7 of 16 (permalink) Old Jun 29th, 2008, 11:19 am
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Quote:
Originally Posted by jacquesvroom
but that separate temperature sensor is only present in older K's—or at least definitely not present in my case!

What passes for logic is this:

a. Bike overheats in slow traffic, especially quickly at stop lights.
b. When you look inside radiator/fan assembly, you notice fan never rotates, no matter how hot engine gets.
c. Disassembly shows fan-motor clearly like buffalo bill—defunct. Plastic stuff melted into brushes, etc. All very ugly and fully permanent-looking in its defunctness.
d. Associated relay also gives very powerful visual indications of similar defunctness.
e. Obtain "new" fan motor and relay. Both work fine separately and together, but not back on the bike.
f. "Feels" like motronic brain also defunct in the area of temperature-sensing-communication. "

"What else could it be???", as we sometimes say here in Texas...

Thanks again for your thought.

Jack Vroom
You might want to check on www.webparts.com parts fiche and look for the sensors that you say are not on your '91 K100. I found a water temp. sensor for a '91 K100( http://tinyurl.com/6jrz2k) under engine/lubrication system/ cooling system-water hoses. Part#61-31-1-459-197 @ $56.87!

Bruce C
'04 K1200RS Capri Blue(totaled)
2008 Triumph Sprint ST

Last edited by brucecha; Jun 29th, 2008 at 11:29 am.
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post #8 of 16 (permalink) Old Jun 29th, 2008, 5:26 pm Thread Starter
 
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I apologize. I mis-spoke/wrote...

I did (foolishly and incorrectly) say my bike doesn't have a sensor as in the picture you sent me. Sorry. I should have said my bike doesn't have a sensor that commnunicates with the fan relay/switch the way the one does in the picture you sent me.

The way my [same as in pic you sent] sensor communicates is through the Motronic.

Weirdly, now it seems the Motronic WILL pass a signal through to the fan when it is generated from a different source [VERY WIERDLY, only 4 times out of 5, though!!]

Now off to check relationship between temperature of coolant and resistance shown by sensor.

Definitely faster and maybe cheaper to buy a new bike!!!???!!!

Thanks again.

Jack Vroom
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post #9 of 16 (permalink) Old Jun 29th, 2008, 5:31 pm Thread Starter
 
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Posts: 7
One other thing...

I could have been more specific about bike as well. It is a '91 K100 RS, 16 valve engine.
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post #10 of 16 (permalink) Old Jun 29th, 2008, 7:20 pm
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Quote:
Originally Posted by jacquesvroom
I did (foolishly and incorrectly) say my bike doesn't have a sensor as in the picture you sent me. Sorry. I should have said my bike doesn't have a sensor that commnunicates with the fan relay/switch the way the one does in the picture you sent me.

The way my [same as in pic you sent] sensor communicates is through the Motronic.

Weirdly, now it seems the Motronic WILL pass a signal through to the fan when it is generated from a different source [VERY WIERDLY, only 4 times out of 5, though!!]

Now off to check relationship between temperature of coolant and resistance shown by sensor.

Definitely faster and maybe cheaper to buy a new bike!!!???!!!

Thanks again.

Jack Vroom
If the fan operation is the bikes only problem.
It might be cheapest(and easiest) to install a separate 12V power source and a toggle switch and relay in your dashboard switch panel! Does the bike have a working temperature gauge?

Bruce C
'04 K1200RS Capri Blue(totaled)
2008 Triumph Sprint ST

Last edited by brucecha; Jun 29th, 2008 at 7:31 pm.
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