1955 brake lights go out with turn signal

[rexbd]

Helping my son with his 1955 tbird. Converted to 12v and negative ground. Lights work great except if try the turn signals then the brake lights go out. Both sides. I replaced the flasher but that did not help.

Also noticed the turn signal switch wont stay engaged it just flips back to the center position. Thinking the switch has gone bad.

 

[Ward 57]

Helping my son with his 1955 tbird. Converted to 12v and negative ground. Lights work great except if try the turn signals then the brake lights go out. Both sides. I replaced the flasher but that did not help.

Also noticed the turn signal switch wont stay engaged it just flips back to the center position. Thinking the switch has gone bad.

Sounds like you will have to pull the wheel and see what's going on. The cancel mechanism is pretty simple and I'm wondering if you missed something in the 12v conversion. It's not as simple as it sounds.

 

[doug7740]

Helping my son with his 1955 tbird. Converted to 12v and negative ground. Lights work great except if try the turn signals then the brake lights go out. Both sides. I replaced the flasher but that did not help.

Also noticed the turn signal switch wont stay engaged it just flips back to the center position. Thinking the switch has gone bad.

Inside the turn signal switch there are two triangles. The wire from the stop lamp is routed to the turn signal switch and out to both tail lights. When the turn signal is engaged, the triangles move to allow power from the flasher to take over and power the brake lights. From what you are describing there might be a large gap between the switch plate and the post that makes the switch slide up and down. Because of this gap the switch is not moving the triangles far enough to power the stop lamps. If this is the case you have three choices for the repair:

• Replace the switch plate
• Squeeze and deform the switch plate to narrow the gap
• Fill the gap with a bushing.

doug7740
1955 Thunderbird Blue

 

[rexbd]

Was able to get the switch to stay in position and not flip back to center by adjusting so that was a big help.

Still having problems with brakes going out.

I have LED rear lights and have tried both conventional flasher and an LED flasher and still same problem brake lights go out every time.

 

[Ward 57]

Inside the turn signal switch there are two triangles. The wire from the stop lamp is routed to the turn signal switch and out to both tail lights. When the turn signal is engaged, the triangles move to allow power from the flasher to take over and power the brake lights. From what you are describing there might be a large gap between the switch plate and the post that makes the switch slide up and down. Because of this gap the switch is not moving the triangles far enough to power the stop lamps. If this is the case you have three choices for the repair:

• Replace the switch plate
• Squeeze and deform the switch plate to narrow the gap
• Fill the gap with a bushing.

doug7740
1955 Thunderbird Blue

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That cancelling plate looks really worn. Wouldn't it be easier to just replace it? I always say repair not replace but in this case I would make an exception as it's not a complicated or expensive part.

 

[Ward 57]

Was able to get the switch to stay in position and not flip back to center by adjusting so that was a big help.

Still having problems with brakes going out.

I have LED rear lights and have tried both conventional flasher and an LED flasher and still same problem brake lights go out every time.

I would look at Doug7740's examination. Pull the cancelling plate and manipulate the switch by hand and see if it's getting the full throw. If the lights work then you know it's not the switch but the actuating mechanism which is easy to replace and adjust.