Bulb holders; intermittency.
Posted: Fri Apr 27, 2018 2:05 pm
I reckon the worst thing to fail an MOT test on is an intermittent bulb-holder. Particularly at the back.
This seems to be a particular problem on cars that are not used very much; simply because the heat from the bulb in use tends to drive out moisture.
Replacement is one solution, and these bulb holders are the same as those fitted to the Spitfire, the Stag and also some Lotus models from the '70s. The Stag Owners Club always have lots of them on their stands at the Shows at a good price but I recently helped to work on a Sprint on which there was nothing lighting up at the back. In this case each bulb-holder's terminals, the connectors, the internal spring connectors all needed cleaning out before it worked.
There was one reversing light which proved to be much more of a problem than the others. The bulb by itself was O.K., the bulb connected across the wiring was O.K.; the contact springs were clean but it still refused to work.
The problem is in the design; the side copper contact that touches the bulb runs up the side of the holder and ends up under the plated mild steel of the surround. If moisture gets in here it corrodes and isolates this ground contact.
Solution: scrape the copper and mild steel clean and run a film of solder between the two. Surprisingly the mild steel solders quite well.
Sorted!
This seems to be a particular problem on cars that are not used very much; simply because the heat from the bulb in use tends to drive out moisture.
Replacement is one solution, and these bulb holders are the same as those fitted to the Spitfire, the Stag and also some Lotus models from the '70s. The Stag Owners Club always have lots of them on their stands at the Shows at a good price but I recently helped to work on a Sprint on which there was nothing lighting up at the back. In this case each bulb-holder's terminals, the connectors, the internal spring connectors all needed cleaning out before it worked.
There was one reversing light which proved to be much more of a problem than the others. The bulb by itself was O.K., the bulb connected across the wiring was O.K.; the contact springs were clean but it still refused to work.
The problem is in the design; the side copper contact that touches the bulb runs up the side of the holder and ends up under the plated mild steel of the surround. If moisture gets in here it corrodes and isolates this ground contact.
Solution: scrape the copper and mild steel clean and run a film of solder between the two. Surprisingly the mild steel solders quite well.
Sorted!
Exactly what I do Tony. I got fed up with trying to get a good connection.