Brake Light

I've rewired a bike and now the brake light works in reverse(turns off when engage the brake). This should be simple, but I can't figure it out. Also, I couldn't get the instrument lighth work work, either. I am trying to rewire this thing from scratch and I don't know what I'm doin. Help!

BTW, this is a 5-wire sachs(Blue/Yellow/Grey/Green/Greenblack).

Re: Brake Light

Does the brake light switch have one wire? And does pulling the brake lever ground that wire to the frame? If so, that should normally complete the circuit, and the light goes on.

but, the brake light is always 'hot' for some reason, most likely an incorrect connection someplace. Pulling the brake directly shorts the brake wire to ground so the light goes off, since the bulb is the path of most resistance, and frame is least resistance. So current will flow through the frame instead of the light element...

but if thats the case, some small current will still flow through that brake light.. It might appear off but not totally off. Try it in a dark room.. Does the brake light glow slightly when the brake lever is engaged?

If you can see nothing, put a volt meter on the bulb contacts and see if current is always flowing. Also check for voltage across the instrument lights.. they might be getting power but most is being drained off..

bottom line is the brake lamp wire is hot when it shouldnt be.. finding and fixing that might cure all the troubles, including the instrument lighting ..

Grab the Sachs manual HERE if you havent already .. crappy but perhaps useful wiring diagram page 32

Re: Brake Light

See Ya Moped Army /

There are two types of brake's that break the ground when the brake lever is pulled, and those that complete the circuit when pulled. You may have installed the wrong type switch or simply one of your brake switches has failed.

Re: Brake Light

Pat Mycrotch /

Hmm..the brake light is definitely "ON" and it defintely goes all the way "Off" when I pedal backwards(pull the spring on the brake switch). The switch came with the ped, but I never had it running prior to this(trashcan find).

The light has three plugs

#1) Grounded to the license plate bolt

#2) Attached to the green power wire

#3) Attached to the brake switch

Brake Switch has two plugs:

#1) Attached to Light

#2) Grounded

I tested the brakelight switch and it's definitely the kind

that breaks the circuit when pulled.

I'm confused with all this grounding stuff. Oh, and I don't

know if this is important or not but comming out of the engine

is another Green wire that I grounded per the numerous wiring diagrams I have. Will this affect how the switch works since the brake light is powered by the other green light?

Also, is there an easy way to test the electrical system without

actually running the bike?

Thanks for your help!

Re: Brake Light

not having that bike and diagnosing this stuff from a distance is practically impossible.. even having the bike in front of you it's tough.

i cant think of a reason any wire coming from the magneto would be directly grounded.. unless the engine is mounted on rubber isolators or something and is electrically isolated from the frame... The magneto is part of the engine and the engine is mounted to the frame and thats the common ground. So, why have a ground wire?

As far as testing switches and whatnot without running the engine, you might try connecting a 6v battery to the circuit in question.. i dont see where that would hurt anything.

Something that needs AC, like the horn, wouldnt work on a DC battery, but you could trace voltage through wires and check bulb activation..

Re: Brake Light

Pat Mycrotch /

I guess that makes sense: I looked inside the holes on the motor mounts where the bolts slide through and they're lined with rubber

Wait....I thought about a 6V battery before but I stopped because I didn't know how to hook it up. Do I ground the negative terminal to the frame and substitute the positive terminal for the "Hot" wire or something else?


Re: Brake Light

the 6v battery could be used you wanted an easy way to see if a bulb was lit or not.

A multimeter set to OHMS or continuity can do the same job, and the meter dial would be the indicator. A multimeter set to ohms actually sends it's own internal battery voltage through the wires.

Put simply, a battery would be connected to opposite ends of the circuit you are checking.. (If the frame is the ground for that circuit, attach [-] battery to the frame. Attach [+] battery to the end of that circuit's 'hot' wire.)


Close the switch and the bulb should light up.

It's all too difficult to describe in words.. there's no subsititute for getting down there and tracing wires and drawing little diagrams and figuring out where the hell power is coming from and where it should be going to..

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account