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MG MGB Technical - Head light troubles

Hi. My dad and I have a 71 MGB GT. The other night I noticed only one of the high beams was working. The next day I tried to go for a drive and neither one of the headlights (neither low beams nor high beams) were working. When I turn the headlight switch on, the blue high beam indicator on the dash lights up and can't control it with the high beam switch, it always stays on. We tested the head lights and they are not receiving power. Does any one have any suggestions on what we should try next? Thanks a lot!
-Lars
LM Lars

Sounds like that often quoted, but rarely is, cause - a bad earth, although that doesn't totally chime with your other symptoms. The high beam light will be glowing when the dipped beam is on if power is getting to the headlights, but because it can't get to earth directly it comes back via the main beam filaments and through the warning light to its earth. The two filaments in series, and particularly being in series with the warning light as well, means there is insufficient current to light the headlamp filaments even dimly. The most likely location for the fault is in the cluster of bullet connectors near the right-hand headlight, which could also be the cause of your original 'cyclops' mode (but on either side) as well as no power to either of them now.

Pull all the wires out of the bullets both sides, polish the bullets, I'd advise replacing the connectors, and use a little Vaseline (or grease or anything similar) on bullets and inside the connectors when reassembling. When pushing the bullets in make sure they go all the way in, they will go so far then reach a resistance, and must be pushed a little bit more to get past that, the lubrication will make that easier. the back end of each bullet must be fully in the *metal sleeve* part of the connector.
Paul Hunt 2010

This thread was discussed on 11/05/2010

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