I am having a particularly troublesome electrical gremlin. My headlight low beam is working the majority of the time. Sometimes it stops for brief periods, but comes back on without any noticeable input by myself. The high beam will not work. It seems a bit of a backstory is in order here.
The bike was born as a 1977 R100S and altered into a RS by the PO. I have had this bike for almost 3 years now and it has performed flawlessly. This fall I decided to service the steering head bearings and add a Toaster Tan Triple Clamp. I'm glad I did, since the bearing were frozen. The bearing and triple clamp replacement went well.
The only issue came once I manage to get the faring back on and the wires reattached. Reattaching these wires was a sizable PITA, as most seemed just barely long enough to reach their connections. Obviously there had been some "adaptations made" in order to accommodate the RS fairing onto a S. Once everything was finally reattached, everything worked just right except for the high beam. I have checked and rechecked connections to no avail. I then order a can of DeoxIt D5 and liberally sprayed the low/high beam switch, in hopes this would help. No luck there. My next action was to install a new headlight switch relay. Same result as the spray. It seems obvious to me that since it worked before I removed the fairing, it almost certainly has to be related to something I did. But I am at a loss as to what to try next. Any advice would be greatly appreciated.
Thanks,
J.T.
Lets visualize the lighting circuit, so we can trace it using a mechanic's probe (below).
• Power goes into the ignition switch on RED. It comes out of the switch on GRAY. This wire goes to one of the fuses inside the HL shell (on the multi-color circuit board) and transforms to GRAY/BLK. GRAY/BLK goes into the handlebar switch, and returns as either YELLOW (Low Beam) or WHITE (High Beam). These go back into the multi-color circuit board where they meet the receptacle for the HL bulb, which has matching colors. There are only 2 YELLOW wires (from the bar switch and to the bulb), but High Beam has 1 additional (3 total) because a wire takes off to the gauge cluster for the High Beam indicator lamp.
• Most likely source of trouble, in order...
- Burned out High Beam (is the Hi Beam dash indicator is working correctly?)
- Issues within the handlebar switch
- Problems with the funky German fuses. (Remove both fuses. Apply Deoxit to the leaves with your finger. Reinstall both fuses.)
- Corroded spade connectors on the multi-color circuit board (Apply Deoxit to each female terminal before plugging it onto the circuit board)
- WHITE wires connected to the incorrect terminal on the multi-color circuit board
• When you're working inside the HL shell, due to the lack of light wire colors are not very clear. The terminals are close together. There is a lot of congestion. I use a floor lamp fitted with 5000K bright white LED bulbs to allow me to see the exact wire color and terminal location. You really can't use your fingers in such tight spaces. Then I work with a pair of "duck bill" pliers to enable me to get the terminals plugged in correctly.
You can easily see that if one of the WHITE wires was mistakenly plugged to another post how easy it would be for nothing to happen.
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
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