brake/signals sharing same bulbs

This is actually for a motorcycle. What I want to do is to remove the rear turn signals and integrate them onto the 2nd filament of the taillight, but dont want the light to stay on when i am turning and braking at the same time.. thanks in advance!

Hi perry,

The second filament is the stop light in which will stay on when you brake, the first is the parking light.

Finally had some spare time to share what I've put together.. It works, but the problem is:

1) When I hit the turn signals, it causes the 2nd filament to blink.. GOOD. But, it also activates the 2nd relay, causing it to shut off 12V from the 2nd filament. GOOD. BUT! when the turn signal goes off, it causes the 2nd filament to turn back on, thus causing it NOT to blink when turning and braking at the same time.. I know its confusing, but yeah.. Thanks in advance relay masters...

How about just using diodes, no relays?  You do lose a little bit of voltage going through the diode, but not enough to be of concern.

So let me get this straight.  You're going to have just one light bulb in the center of the motorcycle, and you want it to serve three functions:  left turn, right turn, and brake.  Correct?  I forsee other motorists not being sure if you're about to turn right or left, but that's a discussion for another day.

Take the brake light wire, cut it in half, and hook up each end of it to a diode.

Take each turn signal wire, and attach a diode to it.  The other end of each of those diodes also goes to the brake light bulb.

I always forget which way the diode's band is supposed to face, but you have a 50/50 chance of getting it right the first time.  If it doesn't work, just switch the diodes around; you're not going to damage anything if they're the wrong way.

Buy the largest diodes that you can as long as they're small enough to work with and are affordable...I'd say 6 amps should be about right.

Just to clarify...he's got a dual-bulb taillight housing.  It would be a bit odd to wire up one bulb to act as left- and right-turn, as well as brake indicator.

If he uses only diodes, he's going to run into the same problem he had when he was using just relays:  When turning or braking, it would be all good; but when turning and braking, the result on the turn-signalling side will be constant-on, nullifying the desired effect of a flashing indicator...

Ah, yes, I see now.

See if you can find wires coming from your turn signal switch that stay on steady; that is, before the output of the turn signal switch reaches the flasher.  The outputs of the switch may be either negative or positive; you'll of course have to test for this.

Attach a diode (facing in the proper direction) to each of the outputs of the turn signal switch.  Tie the other ends of those two diodes together, and use that to drive a relay that will interrupt  the output of the brake wire.

Here's how to wire it up:

85:  connect the two diode-isolated turn-signal-switch wires here

86:  If 85 has a positive, hook this to ground.  If 85 has a negative, hook this to ignition  (Yes, ignition, not constant; you also want the relay to be disabled when the bike is shut off)

87:  empty

87a:  output of brake light switch

30:  goes out through diode and then on to brake light  (Diode may be unnecessary, but it certainly can't hurt.  Other functions of the motorcycle might behave oddly if the bike "knows" that the turn signals and brake wires have been tied together.  Putting diodes on everything will "trick" the bike into thinking that everything is as normal.)