tail light problem on a 34 coupe

34fivewindow

34fivewindow

Senior Member
This is a odd problem, atleast to me, it is. As soon as the engine is running, the tail lights come on, on there own. without engine running, all lights work corectly, with stock light switch on steering wheel. Has anyone else ran into this problem ?
 
Should be easy to find,just track the feed back with a multimeter when the motors going.
Lawrie
 
Does the engine have to be running or just the ignition turned on ? Could be linked to where the feed wire (black with a blue tracer) from the headlight switch tail light position to the instrument light switch for the instrument light is connected under the dash. Should be connected to one terminal on the dash light switch. Maybe its on the ignition switch instead. I expect we are talking about an original 1934 wiring harness here and not some sort of modified car. Regards, Kevin.
 
koates said:
Does the engine have to be running or just the ignition turned on ? Could be linked to where the feed wire (black with a blue tracer) from the headlight switch tail light position to the instrument light switch for the instrument light is connected under the dash. Should be connected to one terminal on the dash light switch. Maybe its on the ignition switch instead. I expect we are talking about an original 1934 wiring harness here and not some sort of modified car. Regards, Kevin.
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Its an older restored 34, 6 volts. with the ignition switch on, engine not running, all lights work as they should. The tail lights come on, as soon as the engine is started.
 
If its only when the ENGINE is RUNNING, then that suggests that the generator is supplying the current to the brake lights. The brake light circuit is independant from the light switch circuit.
 
fordscript said:
If its only when the ENGINE is RUNNING, then that suggests that the generator is supplying the current to the brake lights. The brake light circuit is independant from the light switch circuit.
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Thanks for the reply, I'll look into this in the morning,
 
Yes! I have the same problem. The tail light comes on but very dimly and flickers. I have not trouble shoot it yet. Both the brake lights and the tail lights come on brightly when requested. I'll let you know what I find. I believe it has something to do with the engine vibration and the brake light switch.
 
All the generator does is increase the battery voltage from approx. 6.3 volts to approx. 7.5 volts when the engine is revved up somewhat and the cut out contacts close. This voltage increase in the cars electrical system would not in effect switch anything on as in the stoplights. If your car has its original mechanical brakes then maybe some vibration or movement from the engine starting is actually causing a slight movement on the stoplight switch and closing the contacts because the adjustment on the switch is too fine. Disconnect one wire off the stoplight switch and start the engine to check this theory. The stoplight switch has a small adjustment in its two slotted mounting holes. Regards, Kevin.
 
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