Brake tail light works with the front brake, but not with the back brake.
What would you check first?

 

There's a pressure switch in the rear brake line, It's either the wire fell off or the switch is bad.

 

exactly what he said. Just happened to me.

 

I have the same problem on a 2000 Dyna FXDS-Conv. Guess I'll be looking for this switch and checking the wires and replacing as needed.

 

Appreciate the quick reply....
I probably should have also mentioned its a custom tail light I rewired myself.
Does anyone know if the front and rear brakes have separate wires going to the tail light?
Or, is there just one brake light wire that sends a signal from both places?

 

If it is not what was mentioned above with the brake light switch, you should look at the wiring diagram in your HD Field Service Manual, it is your friend and will help you accomplish many things.

There are 2 separate and distinct switches, one for the front, one for the back, they both feed into the wiring for the rear brake light; unless you custom rewired it, then you are on your own as to what is wrong. Good Luck.

 

Are you running the stock size tire or lowered the suspension?

Taller/wider tire.....sometimes rub on hard bumps and eat wiring under the fender.

I’ve seen that more than once....

 

If the brake light works with the front brake, it is not wiring under the fender...

 

This is like Ground Hog Day !

 

Apparently I can’t read or comprehend...duh😜😜