Regulators can't be adjusted.
Start the engine and then disconnect the + from the battery and measure the voltage between the + wire (in your hand) and the - terminal on the battery.
Also measure the voltage between the + wire and the chassis (bare metal in the battery box will do).
Measure the voltage between the + wire and the engine (you will need a long bit of wire).
All three readings should be the same, between 14.2V and 14.7V (you may need someone to lift the revs above tickover to get above 14V)
Reconnect the battery and read the voltage across the + to - terminal.
It should be the same.
If it drops there is a problem with the battery.
If the voltages are different between the chassis and the engine and the terminals you possibly have an 'earth' fault, (chassis to gearbox or chassis to battery).
White fur ....
https://mechanics.stackexchange.com...e-powder-forming-on-battery-hold-down-bracket