VCCA Home Forums TECHNICAL - GENERAL Electrical - 12 volt 54 3100 electrical brake light issues

Hi everyone! So happy I found this forum. A question please... This newbie just bought a '54 3100, and so here's my newbie issue. My 3100 has dual taillights (2 on each side). When I turn on the lights, 3 of the 4 light up. The only one that doesn't is the top driver side light. When I press the brake pedal with the lights on, none of the brake lights (incl. the top right driver side) light up?? When I turn off the lights and depress the brake pedal, the top drivers side light comes on. So I figure a passenger brake light bulb is bad. I change out the bad bulb with a new1154 bulb. Everything works great for 1 second, then the new bulb burns out... the same filament as the old bulb. There is a 12V battery in the truck, but maybe the truck is still 6V? I'm hoping one of you fine folks will point me in the right direction. Thanks!

The 1154 is a 6 volt bulb. If you truck has been converted to 12 volts you are burning that bulb put very quickly.

I think you want to use an 1157 bulb.

If that bulb is a 6v bulb it's likely others are as well. Who put the 12v battery in? Are you sure it's 12v? If all the bulbs are 6v there's a good chance the vehicle is still 6v and a 12v battery won't play well with it's systems.

Thanks Rusty! I'm out shortly to get some 1157s. Thanks for the input Tiny... I too thought of that after Rusty's suggestion. One of the reasons I used a 1154 bulb is because there's another one on the driver side for sure, cause I saw it. I will investigate whether or not it's been converted, cause I know a 12V battery doesn't play well with 6V components. The previous owner, who owned it for 4 months or so, didn't know, but I do know factually there's a voltage reducer on the gas gauge. When I bought it, I drove it at night for about 45 minutes to get it home, and didn't notice burning wires or smell/see anything. The generator looks like a 6V, but maybe it's a 12V generator?? Still checking... The coil is 12V, headlamp and heater control are 12V. i

Excellent idea to investigate more. Typically (note the word typically) everything but the gas gauge is conveyed to 12 volts in a conversion. There is a reducer installed on the gas gauge. And a resistor added to the ignition circuit.

Let us what you discover.

I'm getting closer... I replaced the upper rear tail lights with 1157's... both brake lights now come on with all the lights turned off. With all the lights turned on, only the passenger brake light works, but not drivers side. This is better, since I had no brake lights with the lights turned on previously. Wiggling the driver side wiring to the lower tail light makes the light go off and on, so I suspect there's bad wiring there, or maybe another 6v bulb. I'll check it out tomorrow morning. Discovered the light switch is 12V. Blower motor has an inline resistor or reducer added to the wiring. And I discovered a loose spade connection to wiring harness on the driver side front fender well towards the front headlight...

Should have given you a Welcome you have come to the right place for answers. Most of them are spot on.

Loose connections and bad grounds are common problems with lights that don't function properly. Dim lights are another indicator. Wiggling, jumper wires, ohm meters, test lights are valuable diagnostic tools when trying to keep those electrons where they belong and happy.

Thanks for the big Texas Welcome! :-) I placed a DMM on the generator (it's a "short case"). At idle it's going 6-7 volts. When accelerator is pushed, I'm getting 12-13V. This may be a 6V generator. but when driven, the ampmeter needle on the gauge moves to "C". At idle, the needle stays right in the middle.

If it's charging over 12v above idle it's not a 6v generator.

If I remember correctly, the six. Volt has a metal band around where the brushes are but the 12volt doesn’t.

Thank you for continuing to respond to our posts and ideas.

I was thinking more about this and have a really crazy idea for consideration. It is prompted by your statement that you have “dual taillights (2 on each side)”.

Could you further describe them?

What has caught my attention is that both the 1154 and the 1157 are dual filament bulbs. I started wondering why you have an additional taillight if there is already a dual filament bulb in the one.

Have you removed all of the bulbs and lock at the sockets? I am interested in they dual post or single post sockets. How many wires go into each taillight assembly?

Thanks for continuing to logically troubleshoot the system.

I am wondering if you have a 6 volt generator mated with a 12 volt regulator. A six volt generator will produce over twenty volts running with the field grounded and no load connected,

is there a Delco tag riveted to the case?

6 volt enerators from 1952 and up did not have a band.

It sounds like the directional signal wiring is screwed up.

Hi Rusty... You stated " I started wondering why you have an additional taillight if there is already a dual filament bulb in the one." I bought the truck in it's present configuration. Top lights act as the brake lights and the lower ones are the turn signals. The lights sit directly on top of each other, 2 to a side.

I have removed the bulbs (all are 1157s), each socket is a dual post, and there are 2 wires going into each assembly.

Hey there Chev Nut! There is indeed a Delco tag riveted to the generator, and it says 12V! :-) It's hard to see cause it's facing down.

I will be the first to admit that I am having trouble understanding the wiring and lighting on your vehicle. It sounds like you have 2 brake lights and 2 turns signals on each side in the rear.

Do both filaments in all of the bulbs light up as expected?

It is confusing, I admit my explanation could be clearer. There are 4 total tail light assemblies: 2 are stacked up on the driver side, 2 stacked up on the passenger side. The filaments mostly light as expected, except with the top assemblies when the lights are turned on... When the lights are turned on, and the brake pedal is pushed, the driver side TOP assembly brake light wont light up, while the passenger side TOP assembly brake light will light up. With the lights turned OFF, all the tail light assemblies work normally, including turn signals and brake lights.

Switch the bulbs from side to side and see what happens.

Looking underneath the bed, there are 3 wires (not in a conduit) going to the rear lights. Old mud and dirt and crusty. They are embedded into clips on the frame, and they look original. Maybe one or more has the insulation worn away., and maybe the cause of this wierdness.

"Switch the bulbs from side to side and see what happens." I put fresh bulbs in which helped a lot, at least it gave me a better situation than the one I originally had. At least I have one brake light working then the lights are on.

This has got to be the most unusual tail light set-up I have ever encountered.

Think of it this way. Every filament in every bulb needs a wire going to it if you expect that filament to light.

There should be 2 wires going to each light. That means 4 wires per side. So there should be a total of 8 wires going to all the taillight assemblies.

Remove the lens from all 4 lights. Watch each filament in each bulb while someone else works the brakes, head light switch and turn signal.

Draw a diagram and label each filament. Then make a note for what action lights that filament.

In a dual filament bulb the brightness (candle power) of each filament is different. For example, in an 1157 the taillight filament is typically rated at 3 candle power and the brake/turn signal filament is rated at 32 candle power. It is obviously brighter.

To paraphrase the old saying, photos can explain a lot. If you could take and post a few pictures of the setup (lights, wire routing, etc.) it would go a long way in helping us understand the issue.

Agree that a diagram and pictures would be a big help including how many wires are coming out of the turn signal switch. If there are only three wires going to the rear, then the truck should have a 7 wire signal light switch. Usually when extra lights were added, they were for a 5 wire switch that needed 2 more wires going to the rear. The 5 wire set up was typical on these early trucks. Could be that someone changed the switch during the 12v conversion and tried to connect all of the add on lights. If it’s a 7 wire switch one solution would be to eliminate two of the rear lights.

Here are some pics. They go in order from the rear to the front.
When the wires exit the conduit, one of them looks to be lamp electrical cord . It is split off and spliced to connect with wires as we move forward. The rear "bumper" is a newer assembly with a license plate holder in the middle. Purple wire goes to the interior dome light.

Let’s just say that you are enjoying the results of the prior owner’s work.

One question. Does the truck have turn signals? If so, how many wires are connected to that switch on the steering column?

I have no idea why there are dual filament bulbs in each hosing. It sure looks like at most only one filament per bulb is being powered. My interpretation of the pictures is that there are only 2 circuits going to the rear.

One is to the tail lights and license plate light. They come on when the headlights or parking lights are on. The other is the brake lights.

I suggest that you need to get a volt-ohm meter and start tracing wires to the terminals in the housings. You will probably need to remove the flexible conduit so you can see how many wires actually go into each housing.

The truck has turn signals. 4 wires coming out of steering column... See image. 2 wires go into each housing.

I suggest that you study this wiring diagram. Based on what I can best determine turn signals were a dealer installed accessory for trucks in 1954. This included adding a second dual filament taillight to the right rear of the bed.

Your latest picture only shows 3 wires in the harness from the steering column. There should be another 3 wire harness going up to the turn signal switch. It has white, pink, and purple wires.

1954 Truck Turn Signals

I am completely confused by the double dual filament tail lights. Until you can trace all the wires to all the filaments I doubt if I can offer much more guidance.

I think what I'll do going forward is rewire where I can, cover/protect it with aftermarket conduits and grommets. What gauge wire is recommended?

The tail lights were wired with 16 gauge wire. This larger wire was used because it was a 6 volt system and it was a relatively long length of wire to the taillights.

If your vehicle is really a 12 volt system and you are not concerned what could happen if someone converts it back to 6 volts, you can use 18 gauge wire.

I would suggest installing new wiring. I would not rely on what you have there.

I 100% agree that new wiring is needed.

I'm down with that! Thanks everyone!!