Electrical issue

JoeMarine

JoeMarine

Senior Member
Gents, can someone educate me on a tail light issue I'm having. I re-wired my entire Model A. I added a passenger side tail light with cross over wires. Here is where the problem is. When I step on the brakes I have the drivers side stop light come on and the passenger "lower" light. The driver side license plate light and the passenger stop light goes out. I checked and rechecked the green and black lines and everything marries up with the correct colors of the wires. Could it be the stop light switch? Mine looks pretty old; may be the original part. Any help would be appreciated. Semper Fidelis
Joe Marine
 
When you added the RH tail light, did you make sure you had bare metal to ground to? If not , you may have to run a dedicated ground wire to make it work correctly. Right now it sounds like it is grounding thru the other circuit. A continuity tester will be your best friend is searching this out.
 
IF...you connect your "crossover"wire to the new tail light the EXACT same was as the one that is there it should work in continuity as you are basically ONLY extending the wires, Get under their and check all that again that you wired exactly the crossover the same and report back to us and as Cal and Jim say, make sure you have a GOOD GROUND..NO pad under the new tail light, metal to metal and check to make sure you dont have a lot of paint and you get a clean connection.....good luck were here to help you...
 
JoeMarine said:
Jim, not to be naive, but can you elaborate. Where do I start looking.
SF
Click to expand...

I'm sorry. What Carl said.

You need good clean bare metal touching metal where the lights mount to the fenders (both of them). Also where the teacup mounts to the bracket, don't forget that.

I use an ohm meter. I read resistance from the edge of the bulb socket inside the light (no bulb installed) over to bare metal, such as the rear bumper. You should read zero ohms. If not, find out why.
 
if the stop light switch was bad the l/s would be inop... as the other s have mentioned make sure you have a good ground..
also by chance if your using fiberglass rear fenders you'll need to supply your own ground.
 
yea id say its got a poor ground.

It IS possible for someone to have connected the wrong color wires inside the teacup light to the wrong spots so you THINK your connecting to the (i dont know, im just throwing out colors and examples) white wire off the brake light when someone actually soldered the green wire to it instead and the white wire to the tailamp. Open the housing up and double check and see if everything looks OK in there.

It is 100% definitely not your stop switch. That is nothing more than having 2 bare wires that you twist together to light up the brake lights.
 
One question before I tackle this. I did buy a rubber pad to install between the tail light bracket and the metal fender. I did it for two reasons: one to match the LH side and the other to keep it from scratching the fender. As mentioned above, could it be that simple? If so, I'll start by removing the pad. I checked all the wires and they all appear to be installed exactly as my wire diagram indicates.
 
You _can_ use the rubber pad, if you want to match the other side. But if you do, you need to make sure that the mounting bolts and nuts give you the required good ground.

The top of the bracket hole where the bolt goes in must be scraped down to bare metal. Inside the hole of the bracket and the hole in the fender should be bare metal. The back side of the fender where the nut goes on must be bare steel. Don't paint the bolts or nuts until tight. A lot of guys on the FB don't like star-type lock washers, but I use them to improve the ground connection.
 
Remove the right taillight lens and touch one volt meter lead to the socket base, touch the other lead to a good ground on the car, or directly to the battery ground. If you have any volt reading (lights on, or brake pedal pushed down) then you have a bad ground.
 
I had a hard time getting a good ground when I installed mine too. Everything is painted individually and then assembled there is a lot of "insulation" between metal-to-metal contact points. I ended up running a small wire pigtail from the fender mounting bolts to a frame member using star type lock washers under the connections, ran the wire in the loom of the wire from the brake light switch, and now it works great.

Steve
 
Last part of the story before I start working. . .this is what the rest of the lights are doing.
1. With the horn and light switch rod turned all the way to the right, I have all four lights illuminated on the two tail lights; and I have both low beams on the head lights illuminated.

2. When I start moving the rod down towards the "6 oclock" position the left headlights go out and the 4 lights on the tail light remain on.

3. when I move the rod down towards around "7 oclock" the head lights go out but the 4 lights on the tail remain the same.

4. when I move the rod the rest of the way to the left, around "8 oclock" the high beams go on. . .same 4 lights on the tail remain on.

5. When I step on the brakes in any position, the top tail LH light stays on but doesn't illuminate as if I were stepping on the brakes . . . and the bottom RH light stays on. Other two lights go out.

6. Lastly, the parking lights on the headlights never come on and I recently replaced ALL bulbs.

Pheww! Hope someone can make sense of this and I'll go to town checking it out.
Thanks again
Semper Fidelis
Joe Marine
 
Doubt this is it, but I was having the strangest things happen with my lights and it turned out to be the wire on the generator cutout was just slightly loose. I took it off, brightened the metal, and hooked it back up...problem solved.

I wouldn't have thought in a million years it was that connection out of those it could have been but I eliminated ALL the other possibilities until I got to that one. I guess it's always the last place you look.
 
Looks like some of the headlight wires are wrong or the switch spider is installed wrong.

Bob
 

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check the length of the horn rod to make sure it is correct, check the connections at the end of the rod to make sure all the solder is tight and wires are there, clean it., check to make sure you have a good headlight ground.. this is important again as everyone keeps stating.
 
I used an ohm meter with the pad on and I had a reading. I took the pad off and now I have a zero reading but the lights are still acting the same. I checked the wires and all the "colors" add up. I'm thinking of mixing the wires to see what that brings.
 
keep those pads off to start, clean the area where metal meets metal GOOD. Clean all the bolts on the Light bar and the horn nuts.. Make sure everything is tight and yes test the wires to see if they are correct..Good Luck
 
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