#MGB Panel lights and Rheostat wiring

There are a lot of wires of many different colours behind the dash and perhaps over the years previous owners have made some mods and changes to add to the confusion.

Dash lighting sub wiring harness with a common earth

Although a colour coded wiring diagram can help they do not always explain the wiring involved on the earthing of a circuit.

Wiring diagram suggesting separate earths

As in this example the wiring diagram would suggest a direct connection to earth for each gauge bulb but in fact the earth for each bulb is taken back within the wiring loom to a common earthing point on the back of the tacho to one of its fastening screws.

Bulb holder showing centre power connection and outer earth connection.

The alternative found on chrome bumper and early rubber bumper MGBs is a wired loop fixed under the gauge clamp knurled nuts which is taken to earth.

1 Comment

  1. My 72 GT does not have a separate earth return for each lamp. Having fitted a refurbished dash, I have had to provide one as the dash was not providing a good earth. I just connected an earth wire between each instrument and then to chassis from the tacho. The dash lamps now work!

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