Packard Forum Index » Pre-War (1899-1942)

Hello,
Still working on my 41 110 coupe. Having an issue with the brake lights. When I drive during the day with the headlights/tail lights off, the brake lights operate fine. When I turn on the headlights/tail lights at night, the brake lights don't come on when I apply the brakes. Any info would be greatly appreciated. Thanks!

I can think of two possibilities. One would be if the tail light bulb filaments are reversed so the tail light is using the bright filament and the brake light is using the dim. If that were the case it is possible the brake lights are working but not seen because the tail light is so much brighter. Not very likely that something couldn't be seen but is worth checking.

If wiring is stock, the power for the brake lights is being supplied via a fuse from essentially the same place the tail light gets its power. A more likely scenario is if both functions are trying to use the same filament or possibly a short is causing both filaments to be lit at the same time. In daylight when no tail lights are on the brake lights can energize the filament. When the tail lights are on the filament is already lit and when the brakes are applied it is like closing another switch in parallel. Since the bulb is already on the brakes can do nothing more.

Look in the trunk (or maybe underneath the car) near the left tail light. There should be at least two connectors similar to the one in the photo connecting a wire from the body loom to one from the left tail light and to a short loom running across to the other taillight. Coming out of the body loom it should be a black wire for the tail light filament and a green wire for brake lights. After the connectors, two wires should enter the sockets to supply the two filaments. Ground is via the mounting of the taillight housing. Not quite sure how turn signals were done in 41 (if you have them) but I think maybe a separate system or if part of the factory wiring, separate bulbs and two more wires out of the loom.

Make sure the brake and tail light wires are in good condition, connected to the proper filaments, and not shorted together anywhere.

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I found that the wires in the left tail light were reversed so I rewired them. This made the left rear light operate properly ,but now the right rear light comes on when the lights are on ,but when the brake pedal is depressed the light goes out and the left light gets brighter. I probably need to buy a rear harness since someone before me got into this and cut it up some, but would like to drive the car some before I get anything. Help!

Not that familiar with where the wire was located in 41s but most cars have 2 to 4 wires in the loom portion going across the trunk. 2 for the tail and stop functions & possibly the gas sender is in a part of it. It looks from the diagram the sender may be a separate wire but if that is included then it usually drops out thru a grommet in the floor somewhere around the middle Turn signals are an unknown. Right side signal could have a wire in the loom or maybe a separate loom was used. The stop and tail wires in the loom should be connected to the same connectors as the left tail light.

If the loom has been worked on and if you can still see any color I would ohm out the loom and verify the same color is used at each end. If no colors are visible then ohm out and see if the same wire appears to be doing the same thing at each end. That might require removing the bulbs and checking that only one contact and it is the same contact in each socket is getting voltage when the tail lights are on. The other contact would get voltage only when the brakes are applied.

Here is a partial 41 diagram showing the connectors and the loom. Note that there are also some straight inline connectors joining two portions of the loom and are located closer to the front. Not sure where those are physically but if a mixup happened there that could be another source of the problem.

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Check that the power gets to the lights at the right times, clean up your grounds and contacts really well, and if you need to splice in a wire fix don't worry about originality but just make it workable. Then you can drive it and have fun!

Thanks for the info. Left side wires were crossed. Right side wasn't grounding. Sure appreciate the info!