Reserve Indicator

[Funduro]

My 2003 R1150R broke down on the road with either a clogged fuel filter or a bad fuel pump. I took it apart, tank off etc., and put a new fuel filter in and it seemed to have fix the problem. When it was apart, with the pump and filter assembly out of the tank, I applied 12 Volts between the ground and the two other terminals of the tank electrical connector. I did this to test the pump and see if that was the problem. The pump ran fine and seemed to be working. The other terminal goes to the float sensor. When I put it all back together the bike runs ok but the reserve light is illuminated. I put about three gallons of fuel in it so the reserve light should be out. I have not ridden the bike on the road but I have given it a good shake to slosh the fuel around to free up the float. My question is, did I fry the float sensor by applying 12 Volts to the float terminal? My options are to finish buttoning it up, ride it, and hope the float frees itself and the light goes off or replace the float sensor or other parts that I managed to fry. Does anyone have experience with the float circuit and understand it's inner workings and do you think I damaged it or is probably just stuck? :blush

[henzilla]

You most likely did damage the sensor by "backfeeding" 12v into the circuit. It is possible to get the float rod in a bind, but not as probable as your first guess is. I would pull it all apart one more time anyways to see for sure. Doesn't sound good though.

[Funduro]

Steve,
Thanks for your input; I wish others would chime in. I agree with you that I might of fried something but this is my latest thoughts. I applied the voltage to the float unit, pump and filter assembly off the bike. I think the float assembly is just a switch that is either on or off. Two things could happen when voltage is applied you would get big sparks and a dead short or an open circuit and nothing would happen. I think I tested it with an open condition because no sparks and no heavy current draw.

This morning I filled the the tank with more fuel to test for leaks and the light is still on. I am now leaning towards a mechanical problem with the switch assembly. I have it back together now and will try to ride it to use up the fuel and test for other problems and then take it apart and study the float assembly. I wish I could find a detailed schematic of the system. My reserve light used to come on after 160 miles. I would also like to find out if there is a position setting that needs to be observed or adjusted for the float assembly? Any information on this problem would be appreciated.

[henzilla]

I have an old one sitting under the workbench...it is more of a potentiometer type "switch". Sorry for the poor picture...looking for my good camera. I have smoked this type of switch before since it acted like a filament with the coils in the widest position.
The float rod is so stiff, you would have to drop it to bend it, couldn't see bending it putting it back in the tank..also no adjustments available..unless it gets bent!

Our 3 different 1150R's averaged a light around 170...+/- if 55 or 85MPH averages running west TX

This site may have a decent schematic...Clymers schematic or Haynes pictures are not really that useful...I just looked

http://www.realoem.com/bmw/select.do?kind=M&series=K82&body=ohne&model=R1150R&arch=0

[Funduro]

Steve,
Well I rode it about 50 miles today and the fuel filter problem certainly seems to be fixed. The bad news is the reserve light is still on with a full tank. I purposely ran over some rough roads to see if I could jar the switch loose and nothing happened.

Thanks for the picture of your set up it was very clear. My unit does not have a float on an arm as your picture showed. This is a R1150R and it only has reserve light and no gauge or RID to show how much is in the tank. The unit seemed to be a rather small white plastic cylinder. I assumed that it housed the float and the switch mechanism. I did not pay much attention to it as I was concentrating on the pump and the filter. I guess I am just going to have to bite the bullet and take it apart again and this time study the circuit and mechanism. I am going to have to see if they sell just that part or must I buy a whole assembly. I am going to check Beemer Boneyard and see what they have.

Thanks for your help.

[Funduro]

This is what the pump assembly looks like. The white cylinder on the left is the float switch.

[henzilla]

We have R1100's and R1150's...don't recall the enclosed housing on the 1150. I do know that was an 1100 plate assy ...maybe I am gettin :gerg:confused: Our R bikes just have the reserve warning...no other display, but I can see where that same unit is used on an RT/GS with a display

Sorry it didn't help any! Good luck on the t-shoot and fix

[kantuckid]

My 2003 1150R reserve light will come on when climbing the steep private road to my place when the bike isn't nearly empty. I get ~ 175 to 200k before a light and go more by the trip odometer, which I reset on every tank. I also use the center stand and always top off to the limit when refueling. You might think about removing the bulb-:brow

[Funduro]

I took the tank off again today to examine the float switch. Indeed that was the problem. Inside that white cylinder is a float that contains a small magnet and moves up and down on a center post. Next to the post is a magnetic reed switch. When the float comes near the magnetic reed switch to opens the circuit and when it sinks down as the fuel drops it closes the circuit and lights the reserve light. When I applied 12 volts across the switch I created a dead short which heated the contacts and gas inside the glass enclosed reed switch and broke the glass envelope. This is an extremely small reed switch about the diameter of a wooden pencil lead. The switch is suspended on its wire connections next to the center post.

Some other interesting information is that the switch assembly has three positions which it can assume on the mounting bracket. My assembly was in the center detente. If you want your reserve light to come on sooner you can move it up one notch and if you want the light to come on with less fuel in the tank you can move it down a notch. The reason the reserve light comes on at different fuel levels on different bikes is the position of the reed switch is determined by not only the mounting position but where it was soldered on to the wire leads that support it.

I don't think you can buy just the float assembly although it does have a BMW logo and part number molded into the plastic cylinder. I purchased the whole pump, filter, float assembly used and will change out the float and put it on my unit. I have few miles on my pump and the filter is new. It is only two solder connections to change it out.

[Acejones]

Over engineered German crap !!