Bizzare Tail light problem

[sultanoswing]

Weird.

My right tail lamp (and brake light) is working just fine.

My left tail light is not working (the brake light is). All other lights are working front and back, and turn signals are all going.

The wierd thing is, when I voltage test the socket, there 11.5 volts across the poles, the earth is good - but the bulb won't light. before you ask - it's not the bulb - I've swapped it out with the other side - and it works, and the other bulb (which works in the right) won't go in the left socket.

Suggestions? /ubbthreads/images/graemlins/confused.gif

 

[MattP]

That is odd. Is the socket damaged in any way? It could be possible that it isn't making good contact at the bottom, but the test leads do. Just a wild guess. And out of sheer bloody-mindedness, have you tried another bulb in the socket? I know that you tested the bulb elsewhere, I was just wondering about the reverse, which might confirm the socket was having trouble holding on to the bulb.

 

[sultanoswing]

Yep - I swapped the right side bulb into the left socket and no dice (or light). You might be right about the contact of the bulb on the points - but the socket looks in good nick to me. I might run a wire from the socket contacts to the bulb contects and see what happens.

...on a (hopefully unrelated) note, I swapped out the ol' glass fuse box (was loose and rusty) for a nice four-fuse blade box. And yes, I did connect the four red wires to the brown wires at fuses 3 and 4) - looks good, feels secure! I mainly did it because a new 'old' box (and its missing cover) was about four times the price.

 

[Nunyas]

the only thing that I can think of is possible there's some unseen defect in the socket that the bulb mounts in that is preventing the bulb from making contact with all of the electrical contacts. Whether it's the socket being warped (slightly oblong instead of round), or the contacts at the bottom being corroded just enough to prevent current flow through the bulb.

I'd try disconnecting the light housing from the circuit, then clean the contact points at the bottom with a pencil eraser.

 

[Dave Russell]

[ QUOTE ]

The wierd thing is, when I voltage test the socket, there 11.5 volts across the poles, the earth is good - but the bulb won't light.
Suggestions? /ubbthreads/images/graemlins/confused.gif

[/ QUOTE ]
The fact that a voltmeter reads 11.5 volts, actually tells nothing about how much resistance there may be in the circuit to the bulb. The average voltmeter would present far less than one milliamp of load to the circuit being measured.

There could be a great deal of resistance in the circuit, the voltmeter would read ok, but the actual voltage would drop to near zero when the tail light load of about four ohms was connected. You would need to measure the voltage with the bulb connected to get a meaningful reading. If you can't get at a socket connection with the bulb in place, push a small straight pin through the wire insulation & connect the meter to it.
D

 

[Bawanadic]

Just read your post and I have seen this problem in several different forms.
The most common being the socket being bad. I get the idea that this was working at one time and then failed. Anyway it's usually a worn set of contacts in the socket, a worn or bent bayonent mount, or a stripped wire that is exposed when the socket is in place.
I normally check the contact by either placing a conductive rated grease on the bulb contacts and ,Making sure I've wiped the socket clean first, I'll insert the bulb and then remove it. If the grease is not compressed, spread around the socket( peaks or swirls ) then your contact are not mating properly. You can also add a dab of solder to the bottom of the bulb contacts, just a small layer, and see if this will improve contact mating.
Even after trying this I always change out the socket..

The preceeding are ways to find bad parts not rejuvinate them.