GS1200SS oil-cooled maintenance and lighting issues brought in for service.
First, the rear brake light (hydraulic) won’t come on. There’s no continuity even when the brake is applied, so it’s a switch failure—replacement needed.
The turn signals are hyperflashing. The relay appears to be standard, so let’s check the bulbs.
The bulb is melted from heat. We should replace it going forward.
It turns out the rear was set up as a position light from the time of purchase. A 21/5W bulb with the 21W side used as the position light—that’s why it melts from heat.
The position light was unwanted, so the wire was disconnected and removed—leaving only the 5W light on, which causes hyperflashing. That’s what was happening.
The headlight low beam won’t come on.
We can trace it from downstream or upstream.
The fuse—the first thing everyone checks—seems fine.
↓
(Furthest downstream) Check if 12V is actually reaching the headlight connector.
↓
After that, just trace the circuit from the fuse onward.
High and low beams share the same circuit. Power reaches the left switch connector and dimmer switch, but when we removed the switch, the solder joint had cracked.
These things do happen. It’s educational and really helpful to learn.
—A side note on inspection topics: when you need a bit more light output, the high beam circuit actually produces higher brightness in terms of the circuit layout. (High beams typically have a different circuit layout.)
After soldering, it’s always better to clean it up.
Flux cleaner is absolutely essential. Skip it and you’ll end up with a mess.
→Sunhayato—maybe it’s just my imagination, but it feels like it has plenty of capacity and gives peace of mind.
Then a light contact conditioner.
→I haven’t done a detailed comparison, but 3M feels reliable.
That covers the electrical work.
