The following relates to a bit of discovery and service work regarding my 1978 R100S but is relevant to all our favorite Airheads...
The R100S came with a rather anemic, single horn. The horn pulled minimum power and was barely a step above just yelling at the "blue hair" in your lane. No horn relay was fitted as was done on the twin horn R100RT and others.
I have a pair of aftermarket horns ready for install on the R100S. Same pair, plus a relay harness, fitted to my R65s and they are very, very loud. With the relay and wiring materials in hand, I figured the R100S would be honkin' in an hour or two.
At least I
assumed so but ya'll know the old saying about assumptions.
My first surprise was when I opened the headlight shell to trace the usual brown/white-tracer wire that supplies power to the OEM horn. A snake's nest inside the shell but what
really caught my immediate attention was a nasty red wire that originates at the starter relay and feeds the ignition switch and headlight relay.
Here's the harness after removal. Cracked sheathing exposing bare wire carrying 12V positive. Couple of spots that appeared to be melted from possible contact with that often troublesome over-heated yellow headlight wire. You can also see the way BMW spliced three wires into one wire. Some sort of pressure/stamping/forging that formed all the wires into a single copper "block". Interesting, that.
I have a few Airhead wiring harnesses squirreled away and was pleased to find a good replacement for this very questionable harness.
The terminal that was plugged into the starter relay and feeds the headlight relay. Corroded terminal connector and only 4-5 strands remain attached with the balance of the wire being broken away. Amazing that the headlight worked at all.
This is what the bottom of the relay connector block looked like when first removed. I relaced this terminal connector block with a fresher one. The larger, red, 2.5mm wire runs from the battery's positive terminal directly to the starter relay. This wire also received a new connection.
Another look at the 1.0mm red wire that feeds the headlight relay from the starter relay. Ugh. Note the use of new, double-crimped terminals such as used on most of the OEM connections. Soldering a connection that is not firmly anchored to prevent flex could result in a fracture or break.
Still another paired wire (blacks) to rehab but almost ready to replace the starter relay and connector block.
After a very busy half-day in the shop, and with everything back in place it was time for the happy dance as Ol' Beck fired right up.
Still need to get that horn relay wiring harness built and installed...
