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MG MGB Technical - another halogen lamp question

Quick question hopefully,

I have a 76B that I took out the original sealed headlights and replaced with halogens. I also replaced the physical light switch with a new one in the cockpit. About 60% of the time the lights look normal to me meaning not to bright and the interior lights look about the same no matter what the RPM. Then every once in awhile the interior lights and the headlamps get almost as bright as my new car. Then about 2 minutes later they go back to the dimmer light. It's kind of wierd. I have check all the basic stuff like alternator belt, switch etc. Does anyone else have something to take a look at.

Josh
Josh

Josh,

Best guess is that you have a loose connection somewhere, or the internals of the headlight switch are getting flaky. Since you've replaced the switch, it's probably not the latter. The way to solve this would be to trace the wiring from the battery to the switch and look for bad connections. The only common point in the wiring to the lights you mention is in the wiring to the switch, and the switch itself, so that limits your search. That is, after the wiring leaves the switch, it travels separate paths to the headlights and the interior lights.

It could be a bad regulator in your alternator, so you might want to drive with a voltmeter attached to your alternator output, and monitor the voltage. It should be 14.6 if everything is OK. If the voltage rises when the lights are brighter, than look for problems in the alternator.


If the voltage doesn't rise, and you don't have bad connection in the lighting circuit, then you probably have bad connections in the alternator wiring.
Dan Masters

If the voltmeter is connected elsewhere - like the fusebox - it will show voltage fluctuations if the alternator wiring has bad connections as well as if the alternator itself is flaky. By connecting the voltmeter in various places like this you can narrow down where the fault may lie.
Paul Hunt

This thread was discussed between 13/11/2002 and 14/11/2002

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