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Cooling Fan Function


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I want to verify that the cooling fan works (after the police battery, siren, lights, etc. were "removed" from the bike) and possibly add a manual fan override switch.

Where is the oil temperature switch? Is this switch also used for an "oil temperature light"? Does the Fan/switch get power from the "Load Relief circuit"? There is a part number (17211342174) found in the Additional Fan and Lubrication System diagrams. Here is a link to a police aux. fan wiring diagram

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The fan temp switch on my bike is part of the engine oil drain plug. You will see two wires attached to the drain plug.

I think it's different on the 1150 though.

I have heard of people adding a manual switch to the fan. Good modification IMO. I would reckon by adding a switch between the wires on the plug, you have a manual fan. I've never heard my fan run nor have I seen the RID show high temperature bars either.

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OK, thanks for the input. I found the switch right next to the oil cooler line attachment on the left side. The switch is normally closed and energized to the control side of the relay by the load relief circuit. The fan power comes from the #2 police fuse.

Now, where is the relay? It does not seem to be in the fuse box.

Also the posted schematic is not quite correct.

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When I bought my 98 rtp, the fan would run all the time, so I just unplugged the fuse.


I would like to have the ability to use it if needed however, so please keep the information coming.

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rgraham, It sounds like you have an open circuit. Check to see if both connectors are attached to the switch. Check the resistance of the switch. It should be closed. If that checks out ok, then you have an open circuit somewhere in the wiring to/from the relay.

I still have not figured out where the relay is located? Does anyone know if there are other uses for the oil temperature switch?

Here is a picture of the switch, it is not the drain plug.



I have simply added a switch (on the dash) to the control circuit that allowing for manual operation of the fan. The oil temperature switch continues work too. No wiring is modified.

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THe only time the fan went on on my RTP was when it was sitting still in the garage doing the throttle adjustments. I had a box fan pushing air on the cylinders but it got warm and when the fan came on I looked and saw the temp had gone to red. That was the only time it ever kicked on. Not even in LAs Vegas 110+ degrees sitting in traffic. Only showed 6 bars then.

If it were really necessary BMW woulda put one on all the RT's. Authority bikes get ugly duty in traffic we don't normally see.

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"...when the fan came on I looked and saw the temp had gone to red."

By red do you mean the temperature gauge (all the bars) was top out in the red? I am trying to figure out if there is another purpose for the oil temperature switch other than to turn on the fan. Do bikes without the fan have this switch?

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  • 1 year later...

Yep, just confirmed that relay 9 is indeed for the fan. What i am going to do is add an overide switch on the dash as i know the circuit and fan both work. My temp switch is as shown in the photo above.

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I just checked my 2004 R1150RTP as I may do the same. I found some differences in the relay locations. The fan relay was the second one in from the left in the middle row. The first one in that row is the horn relay. Both relays are black. I also found the yellow relay on the top row far right is the fog lamp relay and not "not used".



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  • 3 weeks later...

I found the test for the fan operation.


1.Ground Pin 1 of the Diagnostic connector.

2.Turn on ignition (engine off)

3.Hold for 10 seconds.

4.Un-ground pin 1.

The Fan should cycle on/off until you turn the ignition off.

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