all bulbs are working (front and rear)
new turn signal flasher (same issue with the old flasher in so not the flasher)
brake light switch is new.
new bulbs for the turn signal indicators are in and both turn signal indicators on the dash work.

with the brake lights on:

turn the left turn signal on, the right rear brake light stays on

turn the right rear turn signal on, the left rear brake light goes out.

both turn signals work either time, the only difference is the left brake light doesn't stay on when the right turn signal is on.

are both brake lights supposed to stay on when a turn signal is on? the bulbs are dual filament, so I would think that the brake light for the side that the turn signal is on, would also stay on, in other words, for example, if the left turn signal is on, the left brake light would also be on. maybe not though.

any ideas? thanx.

 

It don'st work like that. One filament in the lamp is for turn and brake, the other for tail/marker. Right turn on, only left brake works. All controlled by the turn switch. When no turn is on, brake switch is connected to both sides. When turn is on brake switch is only connected to opposite side. Look carefully at wiring diagram and turn switch.
This is different in modern cars.

 

My 63 98 does this and it is the adjustment of the switch attached to the steering column, I have tilt and the adjustment changes over the years, I wiggle the turn signal indicator arm and the lights work correctly. Now I can see the tail lights in the rear view when driving so I check them all the time.
Steve

 

How about telling us year and model? We can assume this is the 67 in your sig line, but maybe not.

 

thank you for the replies!!!!!!!! Yes, this is the 67 cutlass. so it sounds like it could be the turn signal switch itself.

 

As noted above, the brake and turn signal functions use the same filaments in the 1157 bulb. The taillights use the other filament. There is one brown wire from the headlight switch to the two taillight filaments. This should work independently of the turn/brake light.

The turn signal switch accepts a white wire from the brake switch and a purple wire from the flasher. If the turn signals are not used, the turn signal switch connects the white wire directly to the two wires that run to the turn/brake filaments (green on the right, yellow on the left). If you apply the turn signals, the switch internally disconnects that side from the white brake wire and instead connects it to the purple wire from the flasher. The other side remains connected to the white wire. What that means is that the side not being used for the turn signal remains connected to the brake switch and will be on (not flashing) with the brakes applied. The other side will be flashing with or without the brakes applied. If something else is happening, it likely is the switch.

Note that if the behavior changes if the taillights are off or on, the problem is likely a ground issue at the sockets.

 

thanks again everyone!!! tried what Oldskeeper said about his...turns out if the turn signal arm is in between being fully engaged in the right turn and the neutral position, then the brake light stays on. not sure if that is merely an adjustment or if the switch needs to be replaced. not being familiar with these cars is a hindrance, but I am learning!! I see that you can buy just the turn signal switch part or the whole inner whatever you call it that the turn signal switch part is a part of.

 

that is a lot of good info!!! thanx!!! if you were going to tap into the turn signals to have something else blink with them...which wire would that be? thanx again!!!!!!!!!!!!!!!!

 

took the steering wheel off, determined that the spring clip that snaps into place when the turn signal is engaged is the culprit. seems that on a left turn, the spring end with the bump on it, snaps onto the plane (flat surface) of the plastic "hump" whereas, on a right turn, the bump on the spring clip snaps on the top of the "hump" for the right turn. that takes the switch past where it needs to be to keep the brake light on. If i physically hold the bump on the clip on the plane, then the brake light stays on. I tried to find a way to adjust the turn signal switch to not travel past the "humP' but found no way to adjust it or keep it from going to far. seems, from my research, replacing the turn signal switch on this car is a major undertaking. would love to find another way to limit the travel of the spring clip.

 

That does sound like the turn signal switch in the steering column is bad. They are made of plastic so over time they wear out and sometimes break. They are not too expensive and on a 67 should not be too difficult to replace. Take your time and take lots of pictures of it as you disassemble and you should be able to reassemble it fine. If you have the wheel off and can manipulate the switch, you are pretty much there anyway.

 

Thanx, have tried to see how it comes out. there are three phillips head screws that I thought would loosen it, but does not. looks like the steering column needs to drop, the emergency flasher needs to be removed, possibly the gear selector and then I assume the column can come somewhat apart, but not sure. cannot see at all where the connector is for the switch, again, assuming it is up under the dash somewhere as feeling the plastic cover all the way to the firewall, I don't feel anything in there.

 

ok, got it out. apparently you cannot get it out without taking the pins out of the connector and then cutting off the pins on the old harness. waiting for napa to get the new one...not looking forward to trying to feed that thru if it comes with the pins on. took the gear selector out, but not sure I had to do that. finally found the harness up under the dash and dropped the bracketry for the steering column in order to expose the covers over the harness. what a pain.