Motorcycle Repair/BRAKE LIGHT

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Question
QUESTION: Hello. I have a 2000 Honda CB750. My problem is the brake light. The light works but when the brake is pressed, the brake light does not work. I purchased new bulbs thinking this was the problem but I had the same result. The lights works but not the brake light. I checked the wires and nothing appears broken or disconnected. Any ideas? All other lights work on the bike and I have not other problems.

ANSWER: Hi Ron,

If your taillight fuse is okay then check if you have power to the
brake light switches when the key is on.

There is a black/brown wire that should have battery voltage on it.

There is a front brake light switch near the front brake lever
and another near the rear brake pedal.

Both of these brake light switches should have power to them on the black/brown wire and power
through them to the brake light when you activate either switch.

The green/yellow wire should have battery power with either switch activated and this is
the power that goes all the way to the brake light bulb.

The brake light itself must also be well grounded through the green wire for the
light to work. Check switches for power and then also check the green ground wire.

Make sure the fuse is good and the bulb socket is clean etc.

WS
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---------- FOLLOW-UP ----------

QUESTION: I tried this and all appears to be in working order. I went to my local Honda shop out of frustration and want to know your opinion on what was said and the cost. The Honda shop said my problem was the turn signal relay. They said the part was $70 and labor to install it was $80 for a total of $150. Does this seem expensive? Does it sound like this is the problem or do they just want money from me? Thanks! RON

Answer
Hi Ron,

If your turn signals work then the signal relay is probably okay.
They do cost $70 and labour is likely $80 per hour minimum
to install it.  It is expensive but sounds like the usual shop rates.

The brake light switches only need battery power on one side
and then they simply route that power to the brake light itself
when you push or pull the brake.

It is usually a simple switch on/off circuit.

Maybe you have a break in the wire to the brake light
or a bad ground wire. Both of these can be checked with
a multimeter.

The power can be checked right at the brake switches
and then followed through the switches and on to the brake light bulb.

If you follow the circuit carefully you should find the problem.

The signal relay has little to do with brake lights except
they are both on the same power wire.
If the signals work then the relay is not the problem.

WS
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Wayne S.

Expertise

Licensed Motorcycle Mechanic, Knowledge of motorcycles from 1960 up, Japanese, British and most other brand motorcycle repairs.

Experience

Worked for Yamaha, Honda, Suzuki, Kawasaki British: Triumph, Norton, BSA Other: Most Scooters and Mo-Peds

Publications
Canadian Motorcycling magazine article

Education/Credentials
Licensed Motorcycle Mechanic

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