Author Topic: Wiring a switch to cooling fan?  (Read 14777 times)

Offline bizzaro

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Wiring a switch to cooling fan?
« on: June 29, 2015, 06:13:15 PM »
94 k1100lt........So My cooling fan runs great. Except it doesn't come on! :falldown:  I used jumpers to fire it up the other day and it ran fine.   I have checked the relay with a 9 volt battery and it "clicks".  I also switched the relays around to be sure that was working. So that narrows it down to faulty wiring,  or the  temp sensor.  I am thinking of just hot wiring the fan with a toggle for the Summer and switching it on when the temperature gauge goes above the halfway mark! :dunno I am not a mechanic, and don't know shit about electrical stuff.  Are there reasons that this would not be wise.  I don't want to burn anything else up or destroy anything.  I want to RIDE and will fix it "right" when Winter comes and the riding is over. 
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  • Current:1994 BMW K1100LT Previous: 1982 Yamaha virago 920,1973 Honda CB550,1976 Yamaha 650 Special
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 Bizz

Offline johnny

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Re: Wiring a switch to cooling fan?
« Reply #1 on: June 29, 2015, 06:28:24 PM »
greetings bizzaro...

you letting the temp gauge needle getts into the red...

the bugeye motobrick fan would not kick in until the needle was way into the red...

the burd motobrick fan kicks on when it touches the red...

the brick of the corn fan kicks on a hair left of the red...

j o
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Offline bizzaro

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Re: Wiring a switch to cooling fan?
« Reply #2 on: June 29, 2015, 08:04:08 PM »
And of course, I don't want to blow my motor or relief valve checking out if the fan is working :mbird  Got to be a better way Johnny? I have only had it it in the red once,(at idle) and that spooked me enough to stop.  I figured red was stop? How far do you let it go?  Plus, it runs so much better when it is in the pre halfway mark........or maybe it is just me freakin!

And on that note Johnny,  I got to ask....... about the stop freakin and start motobrickin.........Have I starting motobricking yet?  I have stopped the oil bleeding at both ends.   In under a 1k I have replaced the clutch arm boot. (bleeding in the rear)           Resealed the water/oil pump cause the  dumb ass that rebuilt the pump didn't use "anything" to seal the mating surfaces(bleeding in the front)!!!!!!!!!!!!!!!! :nono           I just put new meat  on the rear.  I went with the oversized Brigestone Battlax T30B radial.  The rear tire size is so limited on this road burner.  And yes, I did all this myself in the last couple of weeks in my open air garage.  I did have someone else replace the fork seals for me.............my mistake. He put in 15w in who knows what quantity! :dunno  I will be changing the fork oil to 10 wt soon along with the matching T30F tire up front.  Running the Metzler Lazertech now which has plenty o life. But like my women, I prefer a matcheing set. :2thumbup: :riding: ok, done patting myself on the back for now. Thanks for listening. 

So is there a way to  fool the sensor into kicking in to see if it is working? The fan runs and the relay is good?
  • Vermont
  • Current:1994 BMW K1100LT Previous: 1982 Yamaha virago 920,1973 Honda CB550,1976 Yamaha 650 Special
See Ya in the Twisties,
 Bizz

Offline johnny

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Re: Wiring a switch to cooling fan?
« Reply #3 on: June 29, 2015, 08:49:55 PM »
greetings bizzaro...

the most easy way to tell if your fan is working is idle it until the fan comes on or until its deep into in the red... if it goes deep into the red and the fan has not come on you gotts to troubleshoot...

or i think its like this...

ignition off... kill switch in run position... ground pin 1... ignition on... kill switch in run position with engine not running...  after 15 seconds unground pin 1... the fan should start and stop and start and stop until ignition is off...



j o
  • :johnny i parks my 96 eleven hundert rs motobrick in dodge county cheezconsin  :johnny

Offline bizzaro

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Re: Wiring a switch to cooling fan?
« Reply #4 on: June 29, 2015, 10:22:17 PM »
Totally lost me there.  The ground pins you are talking about?? Are they at the ignition or the relay?? the relay has 4 blades two perpendicular sets.  Do I pop off the relay and ground out a blade?? Sorry. This is all very new to me. My fan has never come on without me hot wiring it from the battery.  I guess I will  try and overheat it again, but  it seems fool hardy to overheat the  engine to see if the fan is working, and it it is not then WTF.  I do know a guy with one of those heat detecting guns.  You just point it at the object and it reads the heat.  How hot should the manifold read before I need to shut her down(or hopefully the fan kicks in)?...and thanks.







  • Vermont
  • Current:1994 BMW K1100LT Previous: 1982 Yamaha virago 920,1973 Honda CB550,1976 Yamaha 650 Special
See Ya in the Twisties,
 Bizz

Offline johnny

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Offline bizzaro

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Re: Wiring a switch to cooling fan?
« Reply #6 on: June 30, 2015, 07:26:15 AM »
Thanks again Johnny......................your a peach.  I did find all that stuff, except for the last one with the schematics and photos. Got to run off to be a slave now, but  I think I can find a way to check the sensor from that thread.  And just so ya know.......looking back on it, I think my warning light came on when I tried to idle the fan  on and that is when I shut my bike off. 
Thanks Again,
Keep the rubber side down,
BIZZ
  • Vermont
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Offline jimb.

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Re: Wiring a switch to cooling fan?
« Reply #7 on: June 30, 2015, 07:45:54 AM »
 A couple of years ago I faced a similar problem with a fan that worked but it would not turn on when the temperature should have triggered it to. I was scheduled to take the bike on a vacation trip two days from when I discovered I had a cooling fan issue so there wasn't time to obtain a new relay.

I knew it was a faulty relay and not a wiring problem because it's possible to test for that scenario. I installed a switch on the handlebar, interrupted the wiring for the fan that went through the relay then wired the fan to the manual switch. I left things as they were for about two years until I got around to replacing the relay that operates the relay in conjunction with the temperature sensor. The only downside is that I'm sure I operated the fan when it wasn't necessary to do so. After the new relay was installed I put shrink tubing over the quick disconnect terminals that had been added and left the switch on the handle bar and the added wiring in place just in case I need to revert back to manual mode.
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Offline bizzaro

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Re: Wiring a switch to cooling fan?
« Reply #8 on: June 30, 2015, 08:01:14 PM »
Thanks Jimb.  I may  go that route till winter hits.
  • Vermont
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See Ya in the Twisties,
 Bizz

Offline jimb.

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Re: Wiring a switch to cooling fan?
« Reply #9 on: July 01, 2015, 05:12:23 PM »
I meant to add a caution note.

Once the problem has been fixed I suggest that the manual switch be disabled if you are planning to leave the bypass wiring circuit in place. It may be possible that the new replay could be ruined if you energize the circuit with the manual switch when the fan is already in operation.
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Offline bizzaro

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Re: Wiring a switch to cooling fan?
« Reply #10 on: July 01, 2015, 08:31:45 PM »
Thanks. Good to know.  I need to confirm if it is the relay or the sensor and then may go the bypass route till winter.  It is all new to me so you never know when a can of worms will pop up? The bike runs great and I want to burn up the miles.  And not do any damage...................... so I can deal with a manual fan as long as I am  not making future problems. 
  • Vermont
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See Ya in the Twisties,
 Bizz

Offline rbm

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Re: Wiring a switch to cooling fan?
« Reply #11 on: July 02, 2015, 05:45:32 AM »
I meant to add a caution note.

Once the problem has been fixed I suggest that the manual switch be disabled if you are planning to leave the bypass wiring circuit in place. It may be possible that the new replay could be ruined if you energize the circuit with the manual switch when the fan is already in operation.
Wiring the manual switch as detailed in the schematic I provided (see Johnny's reference above) will not damage the temperature sensing relay's circuitry. One method simulates an extreme overheat condition (grounded switched to Terminal "E") and the other parallels the contacts that normally energize the fan.  Neither have long term damaging effects.
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Offline jimb.

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Re: Wiring a switch to cooling fan?
« Reply #12 on: July 02, 2015, 07:32:38 AM »
I'm glad you mentioned that. Sometimes I'm overly cautious.
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Offline noppo

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Re: Wiring a switch to cooling fan?
« Reply #13 on: July 28, 2015, 06:39:22 PM »
i have considered the handlebar switch method, but have not taken action yet.
Frankly, i'd rather not crowd the handlebars on the K1. It's already quite crowded up there.

Has anyone considered the low setting on the Heated Grip switch as a switch for the fan?  Is that a good idea, and would it be straight forward to do so?
:bmwsmile Noppo - Tokyo, Japan. 1992 K1, 2009 GSA, 2007 K12GT

Offline jimb.

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Re: Wiring a switch to cooling fan?
« Reply #14 on: July 28, 2015, 06:53:50 PM »
I have disconnected the manual switch now that I've repaired the fault that kept the fan from coming on. I don't have an opinion on your idea but it sounds interesting.
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Offline rbm

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Re: Wiring a switch to cooling fan?
« Reply #15 on: July 28, 2015, 08:40:43 PM »
Might be possible if you want to disable heated grip function.  This is the switch schematic from BMW for the heated grips.



The switch is a SPDT Center-off toggle switch.  In its OEM configuration, the center pole of the switch has +12V power.  That's not going to work to make the fan spin.  Disconnect the heated grip plug and use the center common (3) and either of the remaining two wires (1 or 2).  One wire connects to E15 and the center to ground.  You'll have to find a way to adapt to the BMW plug on the end of the switch.
  • Regards, Robert
Toronto, Ontario

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Offline noppo

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Re: Wiring a switch to cooling fan?
« Reply #16 on: July 28, 2015, 11:45:00 PM »
Thank you RBM.  Very good to know, and i will keep that diagram.
If i have to entirely disable the grips, then it's a no go.  i need them for winter riding, and i can't let that go.  So, it seems i'm hosed.  All other switches on the bike are in use. It seems that i'm forced to either forgo the fan switch, or clutter up the handle bars. 
:musicboohoo:
i have some thinking to do.
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Offline rbm

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Re: Wiring a switch to cooling fan?
« Reply #17 on: July 29, 2015, 12:15:44 AM »
Why not replace the left hand switch cluster with one from a LT with the green windshield switch?  Use the green switch as the on-off for the fan.

  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline noppo

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Re: Wiring a switch to cooling fan?
« Reply #18 on: July 29, 2015, 05:21:28 AM »
Thanks rbm, but i already did that with the awesome cruise control mod on this site. By far the best mod i've ever done. Thank you though for thinking it thru. 

i do have the option of using the space on the panel next to the ignition. That's where i am now, but have not progressed to the point of taking off the panel to see how much depth i have to work with. This will be interesting.  i may have pics later.
:bmwsmile Noppo - Tokyo, Japan. 1992 K1, 2009 GSA, 2007 K12GT

Offline Scott_

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Re: Wiring a switch to cooling fan?
« Reply #19 on: July 29, 2015, 07:02:40 AM »
You can still do the fan mod with the Low HG switch idea that RBM pointed out. BUT.... with just a couple of changes.

Cut/disconnect and cap the wire for only the low setting going to the grips,(prior to the resistor though) use this power source(when on the low switch setting) to then drive a spst relay coil. Wire the NO of the new relay to the ground circuit of the fan relay like others have done with the manual switch.

You are then in essence installing a "remote" manual switch so to speak.......

On another note, I don't think the LT screen switch wouldn't work for this anyway(without major modification at least) as it is only a momentary switch and you will want a maintained one.
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Offline rbm

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Re: Wiring a switch to cooling fan?
« Reply #20 on: July 29, 2015, 07:05:04 AM »
Good idea with the relay, Scott.  And I didn't realize the LT switch was momentary.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline noppo

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Re: Wiring a switch to cooling fan?
« Reply #21 on: July 29, 2015, 09:45:50 AM »
You can still do the fan mod with the Low HG switch idea that RBM pointed out. BUT.... with just a couple of changes.

Cut/disconnect and cap the <snip>

 :2thumbup: Brilliant, Scott  - Thanks!!  i'm on it.
:bmwsmile Noppo - Tokyo, Japan. 1992 K1, 2009 GSA, 2007 K12GT

Offline noppo

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Re: Wiring a switch to cooling fan?
« Reply #22 on: July 29, 2015, 10:12:28 AM »
Sorry - what does this mean:   "Wire the NO of the new relay"
i think i have the rest of it. Thanks!
:bmwsmile Noppo - Tokyo, Japan. 1992 K1, 2009 GSA, 2007 K12GT

Offline rbm

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Re: Wiring a switch to cooling fan?
« Reply #23 on: July 29, 2015, 06:55:48 PM »
NO = Normally Open.

In automotive relay numbering, this is between contacts 30 and 87.
  • Regards, Robert
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Offline ffbikersa

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Re: Wiring a switch to cooling fan?
« Reply #24 on: November 10, 2018, 06:45:27 AM »
Hello everybody,

According to this topic at K100 forum, the manual switch should be connected between terminals 15 and A2 of the Temperature Switch/Relay unit - but that one exists only at 2-valve K modeld, not at 4-valve like my K 1100???

http://www.k100-forum.com/t10880-manual-switch-for-cooling-fan-for-dummies

Also, did someone try installing an adjustable coolant temperature sensor - which you could adjust to kick the fan on at the lower temperature than the standard 103 deg. C? If yes - where and how to get that sensor?
1997-1999 R 100 RT, 1999-2000 R 100, 2000-2003 R 80, 2003-2017 K 100 LT; now K 1100 RS

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