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MG MGB Technical - Headlights Faulty

The full beam on my 1973 MGBGT has suddenly stopped working. The dip is OK but as soon as I flick to full beam there is nothing, which suggests to me that it is probably not the lights themselves, but something common to them both. The blue panel light comes on though. I wonder whether anyone has any thoughts or experience of this.
Many thanks
Paul Eades

Flakey dip switch? or it is possible that some previous owner put in relays and a relay has given out. Download a color schematic for your car at Advance Auto Wire click on stock schematics and you will have it. This will be helpful in trcing the problem. Good luck - Dave
David DuBois

Don't rule out the bulbs until you have checked for power at the plugs. It is unlikely they're both burnt, but not impossible.

Hi all.

The blue light coming on suggests that the switch is ok.

The first place that I would look would be the bullet connector at the front of the car that splits the single blue / white wire from the switch to feed the two headlamps.



Thanks to everyone with their advice. As an update, I have checked the switch with a meter and it seems to be working fine at the terminal with the blue/white wire leading to the full beam h/lights. However, as suggested I also checked bullet connector/splitter at the front but no voltage there. Seems that there may be an open circuit in the wire itself. Has anyone else had this? Seems unlikely to me that the wire could have burned out or gone high resistance. Any thoughts before I put a replacement cable in?

Paul - as a rule, the wires don't go bad, unless they burn up completely, and that condition is very obvious. The problem is much more likely to be where a connector is attached to the wire. A weak crimp can cause havoc, or a soldered bullet can sometimes break free from the wire, especially if the joint was not well made.

Now, having said that, I once found a heavy power wire that went under a rubber mat in a farm truck, and was embedded in that horsehair padding that carmakers like to use. This wire evidently had a nick in the insulation, because it had swollen up to three times normal size due to corrosion growing within the wire, and aided by the wet padding and a generous amount of fertilizer granules. It looked like a snake that had swallowed a rat, and I had to cut back six inches each way to get past the blue/green corrosion.

So, don't rule anything out - - Alec
Alec Darnall

This thread was discussed between 06/10/2006 and 09/10/2006

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