News:

This message is umop apisdn

Main Menu

Taillight but no brake light

Started by slodoug, Nov 11, 2023, 05:49 PM

Previous topic - Next topic

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?
1983 CB650SC

slodoug

also my turn signals don't blink so that me be related but the switch needs cleaning.
1983 CB650SC

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.
1984 Honda Nighthawk 700S
2012 Honda NC700X
2005 Vespa GT200
1982 Yamaha Maxim 550 (sold)
2006 BMW R850R (sold)
1981 Honda CX500B (sold)

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.
1983 CB650SC

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.
1984 Honda Nighthawk 700S
2012 Honda NC700X
2005 Vespa GT200
1982 Yamaha Maxim 550 (sold)
2006 BMW R850R (sold)
1981 Honda CX500B (sold)

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.
1983 CB650SC

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.
1984 Honda Nighthawk 700S
2012 Honda NC700X
2005 Vespa GT200
1982 Yamaha Maxim 550 (sold)
2006 BMW R850R (sold)
1981 Honda CX500B (sold)

slodoug

im having a hard time just getting the wires out of the back or the front fuse cover face off.
1983 CB650SC

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.
1983 CB650SC