Cable amp rating query
Discussion
Power (watts) = Volts x Amps so a 21w bulb at 12v will nominally draw 1.75 A. However a bulb briefly draws a lot more current when it is initially switched on and the voltage will probably be more than 12v at times so best to at least double that and allow for say 3A per bulb. Probably more of a consideration is the mechanical strength of the wire and durability of the insulation. In terms of a fuse you need to choose one that will be happy with the normal operating current but blow before the cable you have chosen gets hot and catches fire if the system develops a fault. The point being choose a cable that is mechanically and electrically fit for the purpose and then choose a fuse to protect it. Remember that the fuse will have to work two lamps but the cables (depending on how you route them) will not.
Another point. Do yourself a favour and run an earth lead back from the light to some place where you can get a good connection onto the chasis or better still to the battery.
I do lots of rewiring on vintage (and modern) tractors and a bad earth connection (exposed to the elements etc) is almost always the cause of electrical faults - going on fire included.
For indicators practically any twin core (earth and feed) cable with a good bit of copper in it will suffice.
When buying a flasher unit, don't go for the cheapest. Spend a few extrra quid on a good one.
Also make sure you know if the vehicle chasis earth is to the +ve or -ve on the battery, some old tractors are +ve earth and that has caught me out before - only once though!
I'd brought the earths for all the lights - headlamps, side lights, working flood lights etc back to the battery, pushed the battery connectors on only to discover the chasis was +ve earth and I'd brought all my connections back to the negative. It took about 2 seconds for the entire loom to go up in flames! The whole lot needed ripping out and doing again. I was not happy.
I do lots of rewiring on vintage (and modern) tractors and a bad earth connection (exposed to the elements etc) is almost always the cause of electrical faults - going on fire included.
For indicators practically any twin core (earth and feed) cable with a good bit of copper in it will suffice.
When buying a flasher unit, don't go for the cheapest. Spend a few extrra quid on a good one.
Also make sure you know if the vehicle chasis earth is to the +ve or -ve on the battery, some old tractors are +ve earth and that has caught me out before - only once though!
I'd brought the earths for all the lights - headlamps, side lights, working flood lights etc back to the battery, pushed the battery connectors on only to discover the chasis was +ve earth and I'd brought all my connections back to the negative. It took about 2 seconds for the entire loom to go up in flames! The whole lot needed ripping out and doing again. I was not happy.
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