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MG MGB Technical - My lights don't work!

Hi all, a car electrics question (ugh). My high beam did not work, and Summit MG sorted it out (they said it was a poor earth). On the way to Brussels from London yesterday, main beam failed. High beam works, sidelights work, but no mainbeam.

Now, I'm useless with electrics and don't (yet) understand them. However, this would (again) seem to be a problem with a dodgy earth. So:

- how are main beams earthed?
- where do I find the earth connection, to check it?

This, and any other info that would allow me to drive at night again would be really appreciated!

Thank you all for your continual advice. I'm learning that fellow owner knowledge and friendly advice is crucial for owning a 'B!

Resh.
S R Ellawala

I find it strange they said the problem was an earth, as both main and dip work off the same earth. So its either a switch problem or a blown main beam element. What year is the car.
Tatty

Tatty, it's a '69 B roadster, and it has an alternator - thus converted from a positive earth system.. The invoice says "fixed bad headlamp earth". Unfortunately, this is an area I know absolutely nothing about...

Resh
S R Ellawala

By the way, the problem is not the foot operated dip switch - this is brand new (it was the first thing I replaced when the high beam failed, and it made no difference...)
S R Ellawala

The easiest thing to check first then is the following, near the front of the car the loom goes under the bonnet striker panel. there should be connectors on each side, one feeds the left light unit the other the right, the main and dip feed are blue/red and blue/white. swap one side only e.g. blue/white feeds blue/red and vice versa, and only do it with the lights off. then switch lights on, if one side comes on only when you select main, and the other when you select dip, then its the bulbs, if both come on then both go off when switching, its the switch at fault. Hope I make sense.
Tatty

Cheers Tatty - will give this a go. I'm positive it's not the switch unit (although of course it could be the connectors), and I don't think it's the bulbs (both going at exactly the same time?).

I can tell that this is going to be a bit of a pain...
S R Ellawala

Should be easy to fix, like you said "both bulbs", so its most likely a dirty connection, but its best to start any investigation on the electrics from knowing what is the cause and this is an easy test.
Tatty

Resh, welcome to the world of M.G.’s.
I would suggest that you read the following web sites

http://www.mgbexperience.com/service/trouble.html#electrical

http://lighting.mbz.org/tech/how_to/relays/
Maybe you should consider fitting relays?

http://www.teglerizer.com/mgstuff/wirecolors.htm

http://www.mgb-stuff.org.uk/
Click spanners then electrics.

http://www.mgbexperience.com/electrical/lighting.html

Next move I would suggest is to purchase a Haynes manual

Good luck
Ian Holliday

I had the same problem, it was the Lucas double-barrel bullet connectors behind the front grill.

Tim.
Tim Jenner

Whilst fiddling with the ground connection they quite likely wiggled the connector that really was the problem. Because, as Tatty says, both filaments use the same ground is just shows that they do not know what they are talking about. All too common where electrics are concerned. The double connector by the RH headlight with the blue/red wires is the likely culprit, although just because the dip-switch is relatively new doesn't mean it can't have failed already. If you are having problems in this area it is worth replacing all the bullet connectors behind the grill and putting Vaseline in the new ones before inserting the bullets. Also clean the bullets before inserting in the new connectors. As these bullets are only crimped I went as far as drilling a small conical depression in each to show shiny brass and copper, and then filling the depression with solder before reassembling.

BTW 'high beam' and 'main beam' are the same thing. I think you mean 'dipped beam'.
Paul Hunt

Tim & Paul - thanks chaps. It was indeed the Lucas connector, and nothing more serious. Will replace and Vaseline them all as soon as I find somewhere out here in Belgium that sells them. Once more this BBS has proved that the experiences of fellow owners is far more useful than a workshop manual!

And thanks to everyone else who responded - I shall repay the favour as my expertise (?!) grows...

Resh.
S R Ellawala

This thread was discussed between 27/05/2002 and 29/05/2002

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