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MG MGB Technical - Hi-beam indicator lamp

Very near completion of ground-up restoration on 72 bgt. Took the beast on it's first night drive. Noticed that the blue hi-beam indicator lamp gets very hot -- too hot to touch. Is this normal? Bulb is 2 watts. Have new wiring harness and also installed headlamp relays (thanks Paul for the wiring diagram on your web site.)

Get home before dark,
Tom
Tom Custer

I must admit I've never felt the ignition or high-beam lights, but I would never expect them to get even warm to the touch let alone too hot. As far as I'm aware these bulbs as well as the instrument bulbs are either 2w or 2.2w depending on fitting as you say. In the past I've measured the *surface* temperature of these bulbs at 30C, which certainly isn't too hot to touch, and by the time they are in a holder and you are feeling the coloured lens they would be less than that. However that was ordinary *tungsten* bulbs, if you have fitted halogen then I've tested those at 90C - a whole different ball-game. These are recommended for instruments as they give a brighter light, which they do, but they are also *not* recommended for the later 'green film' instruments as they melt the innards!
PaulH Solihull

Tom,

I'm not sure what it is supposed to take, but I think I recall that a lot of dash lights (not strictly MG) are more like 1.2 watts.

Charley
C R Huff

Paul, yes the manual calls for a 2.2w bulb. The bulb I have is the push-and-twist style. Don't think it's a halogen. Is there an obvious difference between a halogen and a regular bulb? I noticed that the metal bulb holder has a red plastic insert. Could this be the problem? Wouldn't think so since it was designed this way.

Please be gentle with me as I'm the kind of guy who seeks advice on whether red goes to positive or negative.

Tom
Tom Custer

No worries Tom.

I can't see the insulator generating extra heat - even though it is red :o).

The only comparison I have between regular and halogen is here http://www.mgb-stuff.org.uk/led.htm. In the top image the halogen has the pointed top, the others not. I assume that is part of the halogen injection process, but maybe not. That's a 6w, there are regular 4w and 2.2w there as well, and another difference is that regular have longer filaments than the halogen. I'm aware of 5w and 3w halogen, but I haven't come across any 2.2w.

I did some experiments with led bulbs as you can see further down that page, which did make the speedo and tach easier to read but not the other gauges. They did give all of them a more attractive blue tint, for me anyway. These run cold of course. The only problem with them is that it renders the rheostat useless (but then why would anyone want to dim already dim lights ...), no problem if you have the simple switch that some years of North American spec had.
PaulH Solihull

This thread was discussed between 17/09/2010 and 18/09/2010

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