1157 bulb question!

Okay, I went and bought some 1157 bulb sockets to convert my rear turn signals to turn/running lights. Those who know this socket will know that it has two leads (one for running and one for brake-the socket case has it's own wire for ground). All the ones I looked at had both filament leads the same color (usually black). Installing them in my old housings was pretty easy (except for pushing the three wires through the little tubes).

But how do I tell which black lead is for the big filament and which one is for the little filament? I can't really see down into the bulbs to see which filament goes to which contact. The bulb uses a bayonet mount, with little pins on the case for locking. Is there a way to reference the contacts to the filaments perhaps by the locking pin position? There must be some standard for this, but I can't find anything on the web. Help!

If you have a battery or a 12 volt power source, you can easily find out which filament is brighter.

Apply the negative battery terminal connection to the ground wire(usually BLACK with YELLOW stripe) and positive from the + battery terminal. The brake light circuit will come on brighter with the running or tail light less bright.

If you got a multi meter or even a test light hook up a ground with either one of the devices.

Turn your headlights/tail light on and find out which wire your getting constant voltage from.

You could also have someone push the brake lever on and off while you test the wires with a multi meter or test light to see which one your getting current on.

I just delt with this like 2 hours ago, i was in the same exact situation hahaha. got it to work too!

You want the brake light to be on the brighter filliment, and the tail light on the dimmer one

I know which power source is coming from the bike, it's which black lead from the socket goes to which filament. I think MFolks has the only real working idea here. Dang! Got them mounted, so I'll have to make up some alligator wires and do it that way. Thanks guys!

polkat wrote:

I know which power source is coming from the bike, it's which black lead from the socket goes to which filament. I think MFolks has the only real working idea here. Dang! Got them mounted, so I'll have to make up some alligator wires and do it that way. Thanks guys!

You got a 50-50 chance of getting them hooked up right anyway. If you connect the power leads and the brake light is brighter than the running light, you win. If not, reverse the power wires and you got it.

You can also just use the the existing 12V lead going back to the tail running light as a source and tap it on each wire from the socket and see which one is dimmer. Use that one for the running light.