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MG MGB Technical - Voltage Range - Dash Gauge Illumination

I know that there are a lot of discussions relating to the gauge lighting in MGB's and my car is no different. I would like to check the reostat to see if it is indeed the problem. Does anyone know the voltage range that I should be seeing at the bulb sockets? I could not find it in the archives. If it matters I have a 73B.

Thanks,
Eric
Eric Willis

Eric

Max should be "12 volts" and it should go down from there.

Larry
Larry Hallanger

You must have at least one bulb connected or you will see 12v throughout the range of turning. With just one bulb out of its socket and the voltmeter probe in it, if that is how you connect the voltmeter, you will see slightly less of a drop than normal but shouldn't make much difference. I have had to replace the rheostats in three cars over the years, they have all been of the printed circuit variety and not a winding on a ceramic former. They have all failed the same way that is part of the printed circuit burns out which means at its maximum brightness setting it is still putting significant resistance in series with the lamps and they are dim. The easiest way to check is to move the wire from its spade to the spare spade on the other connection to the rheostat (in most cases). This bypasses the rheostat altogether and if that makes them significantly brighter you know the rheostat is toast.
Paul Hunt

This thread was discussed between 19/01/2004 and 21/01/2004

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.