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MG MGB Technical - IGN lite

I have an MGB tach in my MGA. No fixture in the can to hold the ign light, just a hole in the can. I need the adapter for the ign light.
Is this an insulated fixture? I ask b/c the ign light has its own return wire and I assume it is not right to ground the bulb holder.
Art Pearse

Yes, it is a plastic fitting.

One side of the bulb is connected to the battery and the other to the generator. There is no ground, as such.
Dave O'Neill2

IIRC it's like a pliable plastic sleeving

you'll also need the jewel lens, on my 'spare' speedo face plate the lens is held by a metal rivet over the lens's cylindrical rear extension with the meal rivet crimping to the back of the face plate and around the lens's rear extension

if that doesn't make sense I can put a photo up

I think the lens might be held so securely because of the flexibility of the joining sleeving to the bulb holder but I might have that wrong as I can't remember
Nigel Atkins

Please do, Nigel !
Art Pearse

If Art has a 4" MGB tach as I suspect it will already have the coloured lens on the front as he says it has the hole in the back for the warning light.

As Dave says you need an insulated bulb-holder with two wires, neither of which should connect to earth anywhere or it will cause major problems. In this respect it is exactly the same as originally on the MGA.

But why do you need this, surely the MGA already has somewhere to mount the warning light? Wasn't this in the back of the original rev counter? And doesn't that light fitting plug straight into the back of the tach?
Paul Hunt

photo anyway as it was asked for, this is just as an example, blue jewel on midget speedo

the white sleeving tube has mostly been picked off before this photo

if it's not what's required then it's not the end of the world just another useless photo, put it on Faceache or Twatter it, it might go viral :)


Nigel Atkins

Actually, i am missing the jewel!

I have an "insulated" bulb holder in the harness, but I checked the continuity between the clips and the inside where the bulb screws - it is the same metal!

Art Pearse

hurrah, just for once I did read the post right

I'm guessing (very dangerous) that the missing white tube sleeving over the jewel was to insulate the bulb holder but as I put I can't remember what it all looked like when I took the gauge apart so I could be wrong

have you got the metal tube (or is it plastic for ign light) (inserted) in the rear of the gauge case that the bulb holder slides into
Nigel Atkins

Nigel, my problem is that I have no tube at all, just the bare hole in the case, and the bulb holder from the harness, which I found would ground if I plugged it in, with disastrous results!
I'm thinking of making a tube out of plastic plumbing parts plus maybe a rolled up paper tube to get to the front. I could even glue a jewel in that. Desperate!
This is holding up my installing the dash and proceeding to test the motor.
Art Pearse

Art dont panic I have one you can have - do you want the MGB type bulb holder as well or are you happy to try to wedge the MGA one on the end of the tube - it ain't pretty but it works - sort of!
Chris at Octarine Services

sounds like you're (also?) missing the bit outside of the can that attaches to the rear of the can to hold the bulb holder then
Nigel Atkins

Chris, I'll take your offer!
Separate email!
Art
Art Pearse

" I checked the continuity between the clips and the inside where the bulb screws - it is the same metal!"

If the holder still has two wires then I'm guessing the original rev-counter had an insulated ring on the back that the holder plugged into.

"Art dont panic I have one you can have "

I hope that's not the short-circuit one ... :o)
Paul Hunt

This thread was discussed between 05/11/2013 and 07/11/2013

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