instrument lighting wiring and fuse

str12-340 said
Well I made a 300mile trip last weekend to a car show at the beach. It rained all the way down, so lights on all the time and no blown fuse!!!!!!
Thanks to all for information and suggestions.

I am curious about one thing. Several of the other fuses are 20 amp (marked right on the fuse box). If you look at the wiring diagram in post #8, they have 14 ga wires on the "hot" side and 18 ga wires on the other (protected) side of the fuse. According to the chart in another post this shouldn't be right. I'm not an electrical expert but am trying to learn - can anybody explain this to me? I get that the 3 amp fuse is to protect the circuit board on the back of the cluster. I'm just trying to be better informed for the next project.

I'll give this a shot. It depends on what you are trying to do with the fuse, whether the loads are constant or intermittent and the air temperature of the wire. Remember I wrote "
The better versions of that are a table or calculator where one also puts in the wire length and how much voltage drop is considered acceptable.
In other words the first consideration is the loss of performance, not the melt dowm of the wire."

Whoever put together that table was clearly most interested in preventing loss of performance - presumable for the LED lampos they are selling.

On our cars, presumably the fuses are there to prevent or at least minimize catastrophic failure.
It's also probably generally more important to keep things running.

Lets look at examples. According to the linked chart a 12 awg wire is only good for 18.6 amps. For good or bad on our cars 12 ga wires often carry more than 18 amps. Heck that 16 ga fusible link routinely carries more than 18 amps. Granted its not usually for long stretches of time, but my point is that it can carry over 40 amps without burning up or even melting its insulation right away.