Harness corrosion.

Front brake switch stopped working...

Disconnected switch and checked continuity. Nada!
Okay faulty switch.

Check voltage to the switch... 12 volts all good.

Jumper the two bullet females to check. Nada!
Rear brake works fine, same circuit.

Hmmm.

Brown bullet male on the switch copper has rotted away internally in the wire. Cut and replace
Switch now has continuity, Woot.

Still no brake light.

Green on the harness female bullet terminal has rotted away internally, cut and replace.

Woot. Brake light now works.

Damn my harness is getting tighter and tighter!

Replaced all the complex connections with Deutsch plugs a few years back but damn if the rest aren't still slowly rotting away.

The old pull the wire trick to see if it stretches is such an important skill on these old bikes haha.

 

I feel your pain, my son has a 2005 Grand Prix. Great car but I've lost track of how many wires we traced down and replaced in sections due to corrosion and breaks. Bikes have been okay so far!

 

I"ve used a few methods to clean contacts in the harness.
Female bullet connectors can be hard to just spray off so I use pipe cleaners
Female spade connectors (flat/curled edges on the other) are the hardest.

CLR foaming spray.

1. Spray, Use plastic brush/pipe cleaner to scrub
2. Spray again
3. Soak
4. Rinse with water
5. Spray with contact cleaner
6. air pressure Dry
7. let sit and dry
   
8. Reconnect.

Vinegar soak

1. Small plastic cup (measuring cup or measuring spoon)
2. Dip the connector in there for 10-30 minutes
3. Remove & clean with water
4. Spray with contact cleaner
5. air pressure Dry
6. let sit and dry
7. Reconnect

Muratic acid
Same as Vinegar but less time, less than a minute and you have to watch it.


If I don't have my compressor handy and I want to use canned air, I blow myself first on it, then use the canned air.

I have an XS650 that had bad voltage drop all the way to the alternator rotor regulator and cleaning all the contacts helped a lot.
Run/Stop switch and start switch on these old bikes are one place that needs cleaning. They have water drain holes that although let water out, humidity and road grime get in.