Dashboard Wiring

[SteveW]

So, I've disassembled the horn/Dip switch for cleaning and painting. I can see where the three wires go for the switch and the one for feed for the horn, but where does the earth wire connect? Similarly with the map light - there is a central soldered connection, but nowhere obvious for the earth.

[Ray White]

I have found Richard Storms to be a reliable and helpful source. He explains that the horn earth is simply a connection to the mounting lug.

Hope this helps:

https://www.mg-tabc.org/library/mgtc-el ... rcuits.pdf

[SteveW]

Thanks Ray, that's a useful document.

I'm still puzzled by the map light though. Mine were attached to the dash by short screws rather than through bolts, so there is no nut to crimp the earth wire under. Maybe I could just solder the wire to the body of the light fitting?

[Tom Wilson]

Map light is held on by one machine screw (bolt) and one wood screw, both round head slotted.
Bolt is 5BA, 1¼ " long. A grounding wire is attached to this on the back of the panel.
Screw is #4 x 1/2".

Tom Wilson

[SteveW]

Thanks Tom. Just one more thing (I'm starting to sound like Columbo). Unless I'm missing some form of insulation, it seems to me that the chrome bulb cover on the map light will be live as it's in direct contact with the bulb holder. Is that correct?

[Tom Wilson]

No, as a live circuit needs to be connected to both ground and live. The cover is connected only to the ground (the base), and the live feed is the purple wire that feeds the bottom point of the light bulb.
Tom