When I turn on the headlight switch - the headlights don’t turn on, and the fuel gauge pins itself to above full mark, and the temperature gauge jumps up to very hot, and the blue full-beam light lights up even though only dip-beam is selected.
But everything works fine with only parking lights on.
Have checked all obvious fuses like gauge fuse, L+R Headlights.
Replaced the combo switch with a spare I had lying around, and get the same behaviour.
Update - it turned out to be a very loose earth connection below the cabin fusebox. One of the 4 earth connections was ultra-loose causing a high impedance connection. When the lights were switched on, the temperature of the connection went up to 67 degrees. I cleaned everything and crimped up the female spade connector onto the earth rail with pliers, and now the temperature is 27 degrees same as all the others. And most important, the lights work
The lights are still a little dim so found that they were receiving +11.0 volts from a battery at 12.2 volts. And the ground side of lights were at 1.2 volts above ground. Out of a possible 12.v volts, lights receiving 10.0 volts, and that wiring both sides of the lights were ‘absorbing’ 1 volt on each side.
And when I connected low volt side of bulb direct to battery 0v, the light brightened considerably.
Have ordered an H4 Headlight Relay Harness Kit from Aliexpress for about USD12 which I expect will improve light output considerably.
