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MG MGB Technical - Flickering igition light

My 77B has now started a new quirk. The igition light begins to flicker on and off ( ever so slightly ) but not all the time. Putting a meter in place it still shows about 12.7 volts output from the alt. Sometimes the light gets a little brighter with the headlights on but not all the time. What gives???
victor gardino

Victor,

You're in the market for a new alternator. The output voltage should be around 14.6 volts. For more info on alternators, see: http://www.vtr.org/maintain/alternator-overview.html
Dan Masters

Whoa! Before you rush out and blow loads of cash on a new Alternator, remove the end cap (two set screws) and inspect the brushes. You'll probably find they're worn out. These can be replaced with the unit on the car. Total cost about 3 quid rather than the 70-odd for an Alternator.
I had the exact same problem a few weeks ago, also a '77 car.
The electronics pack is also available seperately and is worth replacing "while you're at it". Any good auto electrical place that does Lucas alternator rebuilds should be able to supply the bits. Basically, you only need to replace the unit if the bearings (horrible noise, shredded fan belt) or the windings (good brushes, good electronics pack, still no charge) are gone.
Tim Cuthill

Victor, You may want to look at the terminals inside the alternator plug. Several months ago I replaced my 74 alternator two times for a random flickering charge indicator. When I still had the problem after two alternator changes I inspected the plug I found the terminal on the thick brown wire was loose. I soldered on a new terminal and problem was cured. Dan is probably right but it doesn't cost anything to look at the plug.

Tim, In the USA it's hard to find an automotive electric shop that will touch a Lucas alternator. If they will you can expect it to cost about the same price as a rebuild from a parts house. Most shops have no parts for them.

Regards, Clifton
Clifton Gordon

This thread was discussed on 07/11/2002

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