working isn’t the same as correct – Airhead wiring

Otus' headlight bucket threw up

In putting Otus’ headlight bucket back together I discovered that the ground on headlight wiring harness had broken. I went to my parts cache and removed a headlight wiring harness from one of my spare headlight buckets. I made a map of how the original one was installed and connected the “new” harness based on the map. But while I was in there (yeah – “while I was in there” is the phrase that always gets me in trouble) I decided to use more parts from the cache. A little research helped me understand that the auto relay in Otus’ headlight bucket was the reason my turn signal indicator wasn’t working in my instrument cluster. Adding the BMW part would solve the behavior that plagued Otus since he became mine. I wasn’t planning on swapping in a relay but I have two so installing one seemed like the right thing to do. This is where things went bad.

making things right (sort of)

There is a good deal of discussion to be found on the Internets regarding using the BMW turn signal relay versus using an aftermarket automotive relay. The BMW relay currently sells for $81.26. That’s a lot of money for a relay. At some point, Otus’ previous owner had to replace the turn signal relay and chose a basic automotive relay. S/he also moved around a few of the wires in the headlight bucket to make the auto relay work. I found this out when I installed the new Cyclops LED headlight bulb and the starter relay whistled when I toggled on the hi-beam. Whistling relays are definitely not good so I shut everything down and started scratching my head. I also might have had a beer to help clear my head.

a good night’s sleep helped

Although I was disappointed that I was chasing a new issue, I decided that a good think and a good night’s sleep would help. While wiring is not my best friend I did have something on my side – an unmolested headlight bucket! I dug back into the parts cache, pulled out the headlight bucket I hadn’t touched, and carried it to Otus. A side-by-side comparison showed me that, probably to make the automotive turn signal relay work, the previous owner had moved some wires around. I pulled the “new” headlight harness, moved all the other wires in Otus’ bucket to match the unmolested one, plugged the headlight harness back in, and the whistling relay is whistling no more!

what’s the cheapest thing on a BMW?

The moral of this story is that just because something works, it may not be set up correctly. I certainly understand the previous owner’s motivation to use the inexpensive relay. It also appears that her/his understanding of wiring allowed her/him to reconfigure the harness to make things work and save money. The second moral of this story (if there are such things as second morals) is to always remember that the cheapest thing on a BMW is the rider!