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sudden darkness in front


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I have a 2003 R1150RTP twin-spark with 81K miles, of which 18K are my daily commute since I bought it in May.


Last evening on my way home, I found myself abruptly without lights, so I stopped on the shoulder to investigate.


The engine starts and runs. I have the RID and warning lights and windscreen and brake light, but no horn or instrument lights or headlights or fog lights or turn signals or tail light. A visual inspection revealed no fuses burnt; neither did swapping them around cause the problem to move. I also pulled and re-seated all the relays. I consulted the Updated R1150RT Fuse Box Diagram, and my lovely bride helped over the phone by reading the wiring diagram on page 752 of the Clymer manual back home in the garage. (The two references disagree, and neither found the problem.)


After more than an hour of roadside investigation, I rode it along the shoulder and through neighborhood streets to park it for the night at a 7-Eleven. (Thanks to the guy on the Gixxer who saw me, circled back to stop and offer help, then rode behind me so I could benefit from his lights!) I plan to ride it home today, in the daylight.


I currently suspect there's a common ground path for all those lights, not shared by the low-draw electronics that are working. Maybe in the right multifunction switch? I see the Big Safety Issue warning, but I have not yet disassembled the headlamp to investigate. Any other connectors or wear points I should check?


Thanks for any suggestions!

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Morning Bob


Being an RT-P it's about anybody's guess as to what could have gone wrong as some of the RT-P's have some local & specific strange electrical requirements.


But assuming a normal 1150 RT or generic RT-P then my first thought is either a bad LOAD RELIEF relay or a broken/disconnected wire between the load relief relay & the starter solenoid.


You can swap a similar relay into the fuse box load relief relay socket as a test and/or jump the main lighting circuit in the load relief socket for a quick test.


If you have the 1150 wiring schematics (it seems that you do) then ring out the load relief circuit & relay circuit to the starter relay.


You really need to eliminate the load relief relay before moving on to grounds or other places .

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Thanks for the pointer! This seems to have been the culprit. In Doug Raymond's electrical diagrams (which I didn't find during my side-of-the-road searching), this meets my expectation of a shared path to all those loads, though it's on the supply side rather than the common ground I usually find to be the source of electrical gremlins.


Based on the fuse box diagram I pulled the yellow Load Relief Relay, there designated #4. It shows discoloration, as from overheating. It is marked 61-36-6-902-041.


The parts catalog shows this relay type -041 ("Minirelay, make contact, yellow") is used four times, in the positions labeled 4 through 7 in the fuse box diagram, though oddly the parts catalog shows Qty=1 rather than Qty=4. The fuse box diagram depicts the relays in positions 5 through 7 as black, and relays 5-7 in the bike are black, part number -412 ("Mini-relay, NO contact, black"), which is superseded by the yellow -041.


I moved the black relay from position 5 (horn) to position 4 (load relief). My lights now work, and I need lights a lot more than a horn, so I'll be able to get to work tomorrow morning.


I was disappointed the cross-reference lists for both the yellow and black relays omit the donor K100RS and K1100RS under tarps out back. That means I'll have to wait to use my horn until the replacement I just bought arrives from the eBay seller.


Again, thanks for your help!

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Wouldn't it have been cheaper buying it from BMW?

The postage seems excessive to me...or was it a LOT cheaper to ship within the US?


Most importantly, I am glad you have identified the problem and have a solution.

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