Fitting indicator stem bulb difficulty.

[Mr Spigot]

I have been trying to fit a new bulb to my indicator stem (the green one that flashes) but cannot get it to work as the end of the bulb does not seem to go in far enough to reach the terminal at the bottom. The old bulb that went worked fine. I have screwed it in as far as possible but still no joy. I ordered 2 led bulbs and neither have worked. I have checked with a circuit tester and there is a current going to the small terminal inside the stalk. Does the terminal move up and down so it could be jammed at the bottom?
I did wonder about connecting a short piece of wire or spring inside to bridge the gap, although it would probably need to be soldered on to the end of the bulb.

Does anyone have any ideas?

[Sleeper]

LED , the very word rings bells...is the polarity correct?

Have you tested them across a 12v supply?

On mine ( 1958 ) the current flows both ways so a LED would only work for one direction , if at all...

John ;-)

[Mr Spigot]

LED , the very word rings bells...is the polarity correct?

Have you tested them across a 12v supply?

On mine ( 1958 ) the current flows both ways so a LED would only work for one direction , if at all...

John ;-)

Yes, I have tested them and they work. I made sure I ordered the correct polarity. The spare 'ordinary' bulb I have also works but that does not work when screwed in, for the same reason.

[svenedin]

Does your indicator stalk have what looks like a coiled spring in it? On mine the bulb screws in to a sort of spring. It is an absolute devil of a job to get a bulb back out and usually the bulb glass breaks.

[Mr Spigot]

Yes, it is a very tightly wound spring. The old bulb did break when I removed it but the base came out OK. The bulb lengths all look to be the same so I cannot see why the new bulbs will not go in as far.
I tested the circuit and when the spring is connected to the centre contact with a tester, the light flashes as it should when the indicators are flashing.
Photos attached showing the socket and then the bulbs L to R; spare conventional bulb, 2 replacement LED bulbs, broken old bulb. None of the working bulbs work when screwed in and it does look as if the end contact is not reaching the live terminal in the stalk.

The only thing I can think of is to somehow fit a small extension on the end of the bulb to make the connection.

[svenedin]

Well I found the only way to do it was to hold the spring part with small pliers, rotate the held spring so as to open up the coils a bit and then screw in the bulb. This allowed the bulb to screw in far enough. This I had to work out by looking under magnification from a magnifying visor I have for watchmaking. Basically the bulb has a metal lip. This must engage with the coils of the spring. If the coils are not opened out a bit the lip gets stuck on the top of the spring and does not screw in far enough.

Looking at your photo, the other way of explaining it is, the threaded bit of the bulb threads into the spring like a socket but when it gets to the little lip below the glass it gets stuck. You need to move the end of the spring coil to allow that lip to thread in too. Then the bulb will go in far enough to make a good electrical contact

Stephen

[Mr Spigot]

SUCCESS! I did as you suggested and managed to screw the bulb in another millimetre or so and it worked. Not an easy job as 3 hands would have made it so, but just enough to do the trick. I am much obliged to you.

[svenedin]

SUCCESS! I did as you suggested and managed to screw the bulb in another millimetre or so and it worked. Not an easy job as 3 hands would have made it so, but just enough to do the trick. I am much obliged to you.

You are most welcome! I’d never have worked this out without magnification.

Incidentally, getting the bulb out tightens the spring making it very difficult. The same technique can be used of holding the spring in pliers and rotating to open out the coils. A tricky job though.

Stephen