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1Back to top Go down   ['93 K75] Temp sensor relay wiring? Empty ['93 K75] Temp sensor relay wiring? Sun Feb 14, 2021 12:23 pm

roach374

roach374
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I'm doing an m-Unit conversion on my bike, and I want to keep the temperature relay intact (to turn the fan on/off the way it's always done). 

From reading the wiring diagram, I know that:

  • "E" --> temp sensor
  • "31" --> Ground
  • "A2" --> Fan


What I can't seem to figure out are the "15", "32" "A3", and "9" terminals, which connect variously to the fuel injectors, load shed relay, the horn, the fuel injection relay, the ICU, warning lights, and seemingly just about everything else on the bike.

Could someone help me out with some pointers on these three mystery terminals? How do I power this relay?



Last edited by roach374 on Sun Feb 14, 2021 6:13 pm; edited 1 time in total

    

Laitch

Laitch
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@roach374 wrote:. . . I want to keep the temperature relay intact (to turn the fan on/off the way it's always done). 

From reading the wiring diagram, I know that:

  • "E" --> temp sensor
  • "31" --> Ground
  • "A2" --> Fan


What I can't seem to figure out are the "15", "32", and "9" terminals, 
Where's the 32 on this K75 temperature sensor relay from MaxBMW? Can you post a photo of yours?
['93 K75] Temp sensor relay wiring? Scree126


__________________________________________________
1995 K75 81,000 miles
['93 K75] Temp sensor relay wiring? Usa-lo10
    

roach374

roach374
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Sorry, that was a typo on my part. I meant the "A3" terminal. I edited the original post to avoid confusion...

    

robmack

robmack
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15 = Switched power feed input for fan
A2 = power output to fan
31 = Ground
E = water temp sensor input
A3 = Temp indicator on dashboard output
9 = switched power input for module's electronics

There are two power sources required.  One goes to pin 9 and powers the electronics within the module.  The other is a power feed to pin 15 that ultimately causes the fan to spin and is connected to an internal relay that is controlled by the module's electronics.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

roach374

roach374
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Silver member
@robmack wrote:15 = Switched power feed input for fan
A2 = power output to fan
31 = Ground
E = water temp sensor input
A3 = Temp indicator on dashboard output
9 = switched power input for module's electronics

There are two power sources required.  One goes to pin 9 and powers the electronics within the module.  The other is a power feed to pin 15 that ultimately causes the fan to spin and is connected to an internal relay that is controlled by the module's electronics.

Robmack, you're the real MVP. I'll buy you a beer next time I'm in T.O. Thank you!

    

roach374

roach374
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Wait, so is A3 going to be high whenever E is high? (maybe just with different current draw?)


__________________________________________________
1993 K75 standard
    

robmack

robmack
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@roach374 wrote:Wait, so is A3 going to be high whenever E is high? (maybe just with different current draw?)
No, A3 won't be high every time E is high.  The input to "E" is the variable resistance caused by the temperature of the water, which is an analog value over a wide range.  Remember that the temp sensor is a negative temperature coefficient (NTC) resistor (resistance varies inversely to the temperature) so in fact E decreases in resistance the more water temperature increases.   Inside the temp relay electronics, there are some thresholds set.  One threshold is to determine the value of resistance below which the fan will turn on (A2 turns on), and another threshold the value of resistance below which the high temp indicator will turn on (A3 turns on).  The first threshold is higher than the second, meaning the fan will turn on before the High temp indicator will turn on.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

roach374

roach374
Silver member
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@robmack wrote:
@roach374 wrote:Wait, so is A3 going to be high whenever E is high? (maybe just with different current draw?)
No, A3 won't be high every time E is high.  The input to "E" is the variable resistance caused by the temperature of the water, which is an analog value over a wide range.  Remember that the temp sensor is a negative temperature coefficient (NTC) resistor (resistance varies inversely to the temperature) so in fact E decreases in resistance the more water temperature increases.   Inside the temp relay electronics, there are some thresholds set.  One threshold is to determine the value of resistance below which the fan will turn on (A2 turns on), and another threshold the value of resistance below which the high temp indicator will turn on (A3 turns on).  The first threshold is higher than the second, meaning the fan will turn on before the High temp indicator will turn on.

Super informative/helpful, Rob. Thanks!


__________________________________________________
1993 K75 standard
    

NayoAlex

NayoAlex
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Hello. I want to install M unit from motogadget and remove everything superfluous. I don't mind losing the temperature warning light. So you mean I can remove this system and do direct fan start via sensor?


Of course I am with the schemes. But it would help to know that it does not influence other aspects of EFI.


Thanks

    

Laitch

Laitch
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Life time member
The temperature relay is not superfluous.

You might not need the temperature warning light but the engine needs the fan's occasional operation to keep an optimal engine temperature. The temperature relay turns on both the fan and the engine light at specific times based on the signal from the water temperature sensor. If you discard the temperature relay, you defeat part of the system that manages engine heat so you'll need to design or deploy something else to perform its function. 

Wiring the water temperature sensor to the fan will not start the fan and the fan should not be wired to run all the time because that will lessen engine performance then the fan will fail because it isn’t designed to run continually.


__________________________________________________
1995 K75 81,000 miles
['93 K75] Temp sensor relay wiring? Usa-lo10
    

NayoAlex

NayoAlex
active member
active member
Thanks Laitch.

It occurs to me to turn on the fan with the negative offered by the switch.

How it is an NTC, do it through a mini-rele.
On the other hand, all motorcycles work without this relay.

So I will have to look better at the exact function of this relay and if it sends any signal to the switchboard.

As far as I can see it does not. I have verified it through the interactive diagrams.

Thanks again for your input

    

Laitch

Laitch
Life time member
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@NayoAlex wrote:It occurs to me to turn on the fan with the negative offered by the switch.
To which switch do you refer and where is the negative?


__________________________________________________
1995 K75 81,000 miles
['93 K75] Temp sensor relay wiring? Usa-lo10
    

NayoAlex

NayoAlex
active member
active member
Excuse. An error in the translator.

The idea is that the signal that goes to pin E of the temperature relay and that comes from the temperature sensor is used to activate a mini relay to start the fan.

You may think that why remove the original relay to put a mini relay.

And I want to put the bep 3.0 and the M-unit inside the original relay box.

I am also studying how to put an Acewell without the Bep.

And I don't need the coolant warning light unless I choose a speedometer that offers this warning.

Now I am in the ideas phase ...

    

Laitch

Laitch
Life time member
Life time member
@NayoAlex wrote:The idea is that the signal that goes to pin E of the temperature relay and that comes from the temperature sensor is used to activate a mini relay to start the fan.
That's your engineering challenge—finding something to interpret that signal once you've tossed out the temperature relay. Maybe you can adapt your moto to one of Honda's systems, or maybe you just find a larger box and keep the relay.Smile

The coolant light is only needed by riders who want a warning before scalding coolant douses their right legs when their Bricks overheat unexpectedly and then engine shuts down. They probably don't have towing insurance either. Apparently, you aren't one of those riders. cheers 

Please keep us informed about your ideas. ['93 K75] Temp sensor relay wiring? 112350


__________________________________________________
1995 K75 81,000 miles
['93 K75] Temp sensor relay wiring? Usa-lo10
    

NayoAlex

NayoAlex
active member
active member
Hahaha yes. I am not looking for a conventional motorcycle. I'm just looking for a challenge at each point. Like placing R1150 rims perfectly aligned. Benelli tnt 1130 fork and more.

    

Laitch

Laitch
Life time member
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@NayoAlex wrote:I am not looking for a conventional motorcycle.  
This could be your pattern.
['93 K75] Temp sensor relay wiring? Medium12


__________________________________________________
1995 K75 81,000 miles
['93 K75] Temp sensor relay wiring? Usa-lo10
    

17Back to top Go down   ['93 K75] Temp sensor relay wiring? Empty Re: ['93 K75] Temp sensor relay wiring? Wed Apr 28, 2021 10:19 pm

robmack

robmack
Life time member
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Go to the download section of this site and fetch the "Heat Management for K100" document.  Go to the section entitled "Radiator Fan Switch".  That will give you guidance on how to delete the temp relay and replace it with an aftermarket fan relay.  Remember, you're still going to need the temp sensor in the stand pipe on the engine block to get the ignition to work.

The BEP and M-unit are boxes which adapt to the K-bike's sensors and present the information on the gauge.  You're going to need a BEP or something similar to convert some of the signals on the K-bike to signals that are compatible with aftermarket gauges like the Acewell.  Either you buy a box like the BEP or Tenet, my TGPI card or you roll your own circuitry.  In the end, you've got to do it.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Suzi Q

Suzi Q
Life time member
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['93 K75] Temp sensor relay wiring? Medium12Somebody once stuck this picture on one of my build threads too. Probably Laitch, it seems like his kind of sudden left turn  Smile
Thing is, if you can get past the insane colour scheme, there's some outrageous free thinking on that bike.

Edit: Yep it was Laitch. Typical.


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Sometimes I'm not really Suzi Quatro.
    

NayoAlex

NayoAlex
active member
active member
Al principio de los tiempos el mundo era muy aburrido. 
Hasta que un tipo dijo ... ¿Qué pasa si quito este cable? 


Ahí es donde empezó lo bueno ...

    

NayoAlex

NayoAlex
active member
active member
Gracias Rob.


Voy a hacerlo. 
Conozco tu solución hace mucho tiempo. Pero ella no sabía si seguía haciéndolos.


Todas las publicaciones que he leído de tu caja son muy antiguas.

    

Laitch

Laitch
Life time member
Life time member
@NayoAlex wrote:Al principio de los tiempos el mundo era muy aburrido. 
Hasta que un tipo dijo ... ¿Qué pasa si quito este cable? 
Posteriormente, su esposa cobró el pago del seguro de vida y se mudó a Tenerife con el chico de la piscina.


__________________________________________________
1995 K75 81,000 miles
['93 K75] Temp sensor relay wiring? Usa-lo10
    

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