Motorcycle Repair: signal lights blink everything, turn signal switch, brake light switch

Question
QUESTION: I have a 1977 cb125s.
the signal lights work fine except they also flash every other light on the bike including brake lights.
Can you tell me what is causing this?
 Thanks

ANSWER: Don, if you don't have a wiring diagram, you should be able to use one from this site:

http://oldmanhonda.com/MC/WiringDiagrams/MCwiring.php#class  Use CB125-76, which may or may not have the same wiring as the Canadian models.

Pull the headlight assembly to access the wiring connections inside, then look at each and every wire connector to ensure that the wiring colors are all matching exactly.

The power flow for turn signals is: Battery-ignition switch-turn signal switch-L&R signal light strings.

Look carefully for good ground wire connections, especially those underneath the seat which go out to the rear lights. GREEN wires are ground. Bad grounds will cause the current path to switch to another possible source of grounding, which is often back through other light bulbs in the system.

ALSO.. be sure that your battery is a good one, fully charged and that the charging system is operating properly.  With only 6v available any low voltage situations will pull down the power to all the lights and when the flasher kicks on and off, you can see it pulsing the battery voltage in the system, sometimes.

Make sure that your brake light switches are all working properly. If your rear brake light is staying on or the front brake light switch plunger is broken causing the light to stay on, then the charging system will eventually fall behind the voltage requirements of the battery.

Bill Silver




---------- FOLLOW-UP ----------

QUESTION: Just to let you know how and why its fixed now.I believe the wiring is so old it lost its ability to effectively conduct electricity .I relocated the positive wire going to the signal light flasher directly to the batery. This solved the problem of all lights flashing.Thanks for your input.Im enjoying the 77 cb 125 :)

Answer
Don, use caution with using a direct hot wire to the battery. If anything shorts out in the signal wiring, the wires will burn up due to lack of protected circuit. An in-line fuse would be a good idea if you aren't using the ignition switch to control the power to the lights.

Just a thought..  Glad you are up and running with your bike now, though.

Bill Silver