Stop Light Problem

Walt Ebie

Walt Ebie

Senior Member
Not exactly a major problem but since I don't want to drive with only one stop light, I want to get it repaired. Problem: left stop light works fine, so that would seem to eliminate the switch. Right stop light does not light. First thought was a burnt out bulb but I pulled it and the filament looks fine - and I put it in the left stop light socket and it works. Eliminates the bad bulb idea. Checked the wiring (green) and it looks okay from the junction where it splits to serve both left and right sides and I don't see any places where the insulation might have worn through and shorted on the frame. So....I'm thinking about the only thing left is the bulb socket. Can they go bad? Or am I looking at the wring idea? I have not yet pulled the whole tail light off to check the socket but I wanted to bounce this off you guys and get your thoughts. Thanks again.
 
You know the bulb is good so put it back in...use a stick to energize the brake, left light should lite. Take a piece of wire a touch it to the bulb socket on the dead light. Touch the other end to ground, frame or bumper, does it light?
 
Just checked again, jiggled the wires around and, lo.....the light is on. So perhaps I'm dealing with a short somewhere between the junction and the socket - or at the socket. Since I'm going to Snyder's in a day or so anyway. I'll pick up some spare bulbs and a socket or two. I'm sure the wiring and lights haven't been touched since the car was restored back in the early 80s.
 
Simple trouble shooting. If the ground is okay and as J. Franklin says the spring and button are working what is left is the B- wire (hot wire). I always keep jumper wires with alligator clips around. I trouble shoot from what I know is good-backwards.
If you remove the offending bulb you hook your wire to the battery or starter switch. Yes it requires a long jumper, touch that hot wire to the button on the bulb and the brass portion to a good ground...it lights!
Now touch the brass part of the bulb (hot wire on the bulb's button) to the bulb holder and it does not light, bad ground. But what if it does? Good ground.
Inspect as Franklin said, now reinsert the bulb and use you hot wire again; use a sharp point or unfolded staple, whatever and pierce the wire that feeds the bulb. Put your hot wire to the staple
Does the bulb light up? Yes...then it most likely is the wire that feeds the bulb.
It if it doesn't lite up the problem is not backward but from that point forward. In other words the bulb holder, spring or fiber insert even the bulb itself.
Don't trust bulbs. Flick it with your fingernail and watch the filament.
 
More like an open. Roll up some sandpaper an clean the inside of the bulb holder and button. Dremels work good. Pull the hot wire and see if the spring is working. If the bulb is working after that, apply light grease and be done.
Replacing stuff complicates matters IMHO.
 
Here is an easy way to clean the inside of the bulb holder:
find a round wire brush used to clean the inside of a 1/2 inch diameter copper line.
hardware stores have these.
usually a handle on the other end.
It will remove any corrosion with a few twists inside the bulb holder.
Bob
 
FWIW:

On any old vintage vehicle, if your taillight(s) or stoplight(s) are not working, and you have not tried grounding the taillight fixture & bulb from a known grounded source .......... just go watch TV until you feel like checking the ground.
 
The term, SHORT, is too often used Incorrectly, as the cause of a problem. A TRUE SHORT is like current being "GROUNDED" to metal & causes SMOKING, OVERHEATED WIRING, BLOWING FUSES, ETC.
Sounds as though you just have a POOR/LOOSE/CORRODED connection.
Bill W.
 
How and where did you join the right brake light to the left side?
Check there for a poor connection. Those squeeze splicers aren't the best way to go.
 
In my experience on all kinds of vehicles (not just Model As), when chasing the open circuit, people tend to focus on the bulb and then the supply wires. It is common to neglect the chassis, which usually turns out to be the problem. Both car paint and corrosion (rust) are enemies of current. The socket can corrode. The socket is simply pressed into its housing, which can be problematic. The housing is screwed to the mount. The mount is bolted to the fender. The fender is bolted to the body. The body is bolted to the frame. The frame is connected to the battery. Every one of these connections between bulb and frame is a likely place for your open to occur.

Expanding on what Willie Krash said, when troubleshooting an issue like this, I'll use a long piece of wire from the chassis-connected side of the battery around the car to the bulb, then the socket, then the housing, the mount and so on. Once the un-grounded part is located, fix it as necessary.

-Kyle
 
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