Voltage gauge troubleshooting

[ghodges]

Hi everyone

I have a 2004 Blue Bird TC2000 and I need to track down what's happening with the voltage gauge on the instrument panel.

When the engine is running the gauge will usually show either 0v or be pegged out at over 16v.

I put a multimeter on the batteries while it was running and it read 14.3v which is what I would expect.

So I'm unsure how that gauge works and what part(s) need(s) to be replaced. Does it get a direct reading from the alternator/batteries or is there a sending unit somewhere that feeds that gauge in the instrument panel?

Thanks for your help - Gary