17-11-2019, 02:51 PM
Hi Colin
The headlight current returns via the metal of the body/chassis, via any bolted joints such as the front wings. Since the earthy side of the battery normally connects to the engine block (at or near the starter motor) there must also be a link to join the engine block to the body. With a rubber mounted engine this link may only be provided by the copper petrol pipe and the bolts holding the tank to the chassis. Many owners fit an additional braided strap between engine block and body, or fit a lug midway along the earthy starter cable and bolt it to the battery/tool box.
As others have said, using a voltmeter across any switch, joint or junction will show up excessive voltage drop when the circuit is switched on. I would aim for less that 0.6 volts total drop in the entire feed and return circuits, i.e. less than 10% of battery volts.
The headlight current returns via the metal of the body/chassis, via any bolted joints such as the front wings. Since the earthy side of the battery normally connects to the engine block (at or near the starter motor) there must also be a link to join the engine block to the body. With a rubber mounted engine this link may only be provided by the copper petrol pipe and the bolts holding the tank to the chassis. Many owners fit an additional braided strap between engine block and body, or fit a lug midway along the earthy starter cable and bolt it to the battery/tool box.
As others have said, using a voltmeter across any switch, joint or junction will show up excessive voltage drop when the circuit is switched on. I would aim for less that 0.6 volts total drop in the entire feed and return circuits, i.e. less than 10% of battery volts.