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MG MGB GT V8 Factory Originals Technical - Voltmeter

I plan to fit a voltmeter to my conversion(1978 RB GT)
Does any one have a wiring diagram for the elec. hook-up?
Thanks Trevor Burnett
t burnett

Any ignition feed and earth. Preferably fused i.e. a green wire of which there are many behind the dash, unless the voltmeter has its own in-line fuse in which case a white, round the ignition switch area. Earth can be picked up from the thumb-screws holding in any of the existing gauges, or any convenient screw into bodywork. If it's illuminated than you will also need to tap into a red/white wire going to the bulbs of any of the other gauges.

As an alternative you could wire it into the accessories circuit at the ignition switch (white/green, which is unfused so really needs an inline to the voltmeter), then you can watch your voltage drop while you are parked listening to the radio.

Be aware that white, and particularly green, and particularly when there are a lot of electrical things switched on will show a lower voltage than the alternator and the battery, due to voltage drops through the myriad 30 year-old connections in the white, brown and green circuits. It rather makes the fitting of a voltmeter a bit pointless if it's showing one or two volts less than the alternator and battery. The only way round that is to have an ignition powered relay connecting the voltmeter to the brown at the solenoid. In a sense you are fortunate in that is what you already have - almost - so connecting the voltmeter via an inline fuse to the white/brown at the ignition relay would be the best place to go.
Paul Hunt

Thanks Paul,I knew I could rely on you

Rgds Trevor
t burnett

This thread was discussed between 28/10/2009 and 30/10/2009

MG MGB GT V8 Factory Originals Technical index

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