1955, wierd tail lamp wiring problem

[Capt. Chris]

Looking for a little help with a weird wiring problem on a 55: When the ignition is turned on, the tail lights go on, even if the light switch is off. The headlights and parking lights are not effected. I have been through the wiring diagrams, and followed the wiring (except where hidden in the interior area, and cannot find any apparent cross-feed for the current. I am thinking the light switch may be bad, but all lighting functions work properly when switched on. Thinking it might be back feed through a bad ground?

Has anyone experienced this before? Looking to troubleshoot, not rewire the car which is a 100% original, low mileage, six volt car car. Any thoughts or suggestions will be appreciated. Thanks.

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[doug7740]

Chris,

If the headlight switch is in question it can be easily tested with an ohm meter.

Disconnect the battery and take headlight switch out by pulling the shaft out after pushing the small plunger on top center of the switch. The plunger is the only thing on the headlight switch that has no wires attached to it. After the shaft is removed, unscrew the nut from the front side that holds the switch in the dash.

With the battery still disconnected and switch hanging where you can see it, connect an ohm meter from terminal B (yellow wires) to terminal R (black wire for taillights). You should only have continuity with the headlight switch in the parking or headlight position. If you get continuity when the switch is in the off position the switch is faulty, replace headlight switch.

Since you mentioned that all of the lights work properly, I don't think you have a back feed through the ground. Do the brake lights work properly?

Doug
1955 Thunderbird Blue

 

[Tech writer 60]

Looking for a little help with a weird wiring problem on a 55: When the ignition is turned on, the tail lights go on, even if the light switch is off. The headlights and parking lights are not effected. I have been through the wiring diagrams, and followed the wiring (except where hidden in the interior area, and cannot find any apparent cross-feed for the current. I am thinking the light switch may be bad, but all lighting functions work properly when switched on. Thinking it might be back feed through a bad ground?

Has anyone experienced this before? Looking to troubleshoot, not rewire the car which is a 100% original, low mileage, six volt car car. Any thoughts or suggestions will be appreciated. Thanks.

Look for a bad Brake light sw. Yes I know id should be wired Battery hot but, someone may have wired it Ignition Hot.

 

[Martin P]

Chris,

If the headlight switch is in question it can be easily tested with an ohm meter.

Disconnect the battery and take headlight switch out by pulling the shaft out after pushing the small plunger on top center of the switch. The plunger is the only thing on the headlight switch that has no wires attached to it. After the shaft is removed, unscrew the nut from the front side that holds the switch in the dash.

With the battery still disconnected and switch hanging where you can see it, connect an ohm meter from terminal B (yellow wires) to terminal R (black wire for taillights). You should only have continuity with the headlight switch in the parking or headlight position. If you get continuity when the switch is in the off position the switch is faulty, replace headlight switch.

Since you mentioned that all of the lights work properly, I don't think you have a back feed through the ground. Do the brake lights work properly?

Doug
1955 Thunderbird Blue

Hi Doug:
quick question: I have successfully installed LED rear Light Conversion all was working properly except the left Rear Running Light stopped working, seems like it may be a short either at the Socket or another location associated with the Drivers side rear tail lamp. Blinkers work on both sides, stop lamp functions, just the running light on that one side?? Any suggestions on where to start? Is the wire associated with that one side different than the right side?

 

[doug7740]

Hi Doug:
quick question: I have successfully installed LED rear Light Conversion all was working properly except the left Rear Running Light stopped working, seems like it may be a short either at the Socket or another location associated with the Drivers side rear tail lamp. Blinkers work on both sides, stop lamp functions, just the running light on that one side?? Any suggestions on where to start? Is the wire associated with that one side different than the right side?

Martin,

When the headlight switch is in the park or headlight position, battery voltage is present at the “R” terminal of the headlight switch. There is a black wire connected to the “R” terminal which connects to the transmission selector light, (if equipped with an automatic transmission), the license plate lights, the left tail light and right tail light.

If your license lights and right tail light are working, then the problem is either where the left tail light connects to the black wire or the left LED light is defective. Since the turn indicators and the stop lamps are working, that would indicate that you do not have a ground problem.

With the parking or the headlights on, check for battery voltage where the left tail light connects to the black wire. If you have battery voltage at that point, then the left LED light is defective.

doug7740
1955 Thunderbird Blue