Taillight but no brake light

[slodoug]

1983 CB650SC
Brake light doesn't come on but taillight does. I have tested all fuses and all are ok. I followed test of taillight indicator light and that is fine. Indicator comes on if the bulb is removed or either tail or brake wire are removed. I have tested 3 1157 bulbs (2 used 1 new), all work as taillight and both light up the brake filament if inserted backwards so bulbs are ok, fuses ok, something is not triggering the brake wire. Front brake switch has 12v to ground. If I short that with a paper clip, nothing. Rear brake switch has 12v to ground, nothing. I get like 7v voltage on the brake light when those switches are pulled. I'm thinking it has to be a bad brake light sensor box. What else can I try?

[slodoug]

also my turn signals don't blink so that me be related but the switch needs cleaning.

[mollusc]

Is it possible to unplug or bypass the sensor box in order to eliminate that from the circuit?  I know that I did something with mine when I converted to an LED rear light, but I forget exactly what it was.

[slodoug]

I dont think so, the sensor unit controls the taillight indicator light on the dash, which does work. I ordered a repl. sensor and a repl left switch.

[mollusc]

The check unit doesn't work with LEDs so my dash light was always on.  I don't remember if I just took the bulb out of the dash or if I removed the unit entirely.

[slodoug]

update: the fuse box seems to be the culprit here. got it working momentarily then it went out again. rear turn signals i'm replacing, the right is so corroded i cant remove the bulb. Gonna tear out the fuse box today, maybe repaint the cover and headlight while I have it off.

[mollusc]

I seem to remember people having issues with the CB650 fusebox.  There may be an aftermarket option.  I had to do a full replacement on my Yamaha -- seems like all the Japanese companies were using rotten electrics around that time.

[slodoug]

im having a hard time just getting the wires out of the back or the front fuse cover face off.

[slodoug]

got the fuse box out, one of the metal tines holding the fuses in broke so i ordered a replacement. Would love it if someone has a step by step DIY for relocating and replacing that archaic box.