Rear brake switch / smoking wires

[Guest]

so I happened to ride in the rain yesterday and now noticed today that I am having some major issues with the rear brake being applied and something shorting out the wires. I tested the switch and sure enough it is faulty, but now that I replaced the switch I'm experiencing the same problem, only after it working for about 2 minutes. What do you think is causing the wires to get so hot they are melting the plastic. this only recently started happening.

[daturat100r]

Check ya fuse ratings for starters

[chef1366]

Bad ground. Find an eye wire grounded around the battery box and clean it. I usually move it to a more solid grounding area like the frame.

[A74R1]

Ground seems good from the battery to the frame.. good contact and everything..

Do you think that it could be related to swapping out the tail light with a 2 wire model and not connecting up the other "green" wire that was to the original tail light?? Also, haven't got around to installing the rear turn signals so there are a couple black wires not connected back there as well.. Every the rear brake is applied something is shorting out even with the new switch...

[Steve]

Do you think that it could be related to swapping out the tail light with a 2 wire model and not connecting up the other "green" wire that was to the original tail light?? Also, haven't got around to installing the rear turn signals so there are a couple black wires not connected back there as well.. Every the rear brake is applied something is shorting out even with the new switch...

Any chance this problem showed up about the same time as the new light?

If you now have a 2-wire model, what did you give up, tail light or brake light?

There is nothing in the switch that will draw any excess current, it only controls what is "downstream", like a LIGHT. Find out what wires are supposed to go to your light, connect them.

Depending on which black wires are floating around at the back, you might have problems, but only if you use your left turn signal.
There are two black wires with white stripes. They are the ground wires for the turn signals, and there will be no problem if they are not connected. The turn signal wires are green for the right side, solid black for the left side. If the end of the black wire is not insulated and you activate the left signal, it might short out, but will not harm your brake switch in the process.

.

[Flyboy]

You say you changed the rear light?
Check your connections, bets are you have one wire to 12V and the other wired to a ground wire, so every time you push the pedal and close the switch you are creating a dead short, 12V directly to ground.

[A74R1]

You say you changed the rear light?
Check your connections, bets are you have one wire to 12V and the other wired to a ground wire, so every time you push the pedal and close the switch you are creating a dead short, 12V directly to ground.

This has got to be what it is... It had been working for quite awhile but now seems to be melting the wires every time.

The light I installed is a standard trailer light with running light and brake light, which was working just fine, but the original light did have the 3rd wire in which I never have attached to anything.

Just rechecked the wiring and I only have the brown and the white tail light wires hooked up.. the 3rd, black with white stripe is not connected...

How else would someone hook up the 2 wire tail lights... seems like all of them nowadays are only 2 wire..

[Flyboy]

Firstly download a wiring diagram for your bike if you don't already have one.
You will find one on Basscliff's amazing site here

http://members.dslextreme.com/users/bikecliff/

Think of your brake light switch as exactly that, a switch it either breaks or completes the circuit on either the live side or the earth side of the circuit.
On the GS it is on the live side, so one wire goes to a 12V source and the other to the tail light, when the switch closes the contacts touch and current flows to the bulb.
Release the brake and the contacts move apart, breaking the circuit and no current flows to the bulb.
If your light has a double filament bulb (one for ail light and one for brake light in the same bulb) and only two wires, one is +12V for tail light and the other is +12V for brake light, the unit goes to ground through its mounting.
So make sure the unit is not mounted on a plastic fender, but to some part of the frame.
If you need to you can run an earth wire from one of the mounting bolts of the light to one of the bolts on the frame anywhere, with eye terminals.

Hope that makes sense.

[Flyboy]

What bike is it?
I suggest you put your bike bike in your signature so we don' have to keep asking everytime or play guessing games, just makes life easier.

[posplayr]

If the new light is drawing too much current he can control the light using a relay. The brake light switch powers the coil to operate the light which would be a lower load on the switch.