Purpose of a fuse is to prevent a fire or other damage if circuit should short or otherwise draw excessive amps.
A 22 gauge wire can only handle 8amps(@12v), if you used a 10amp fuse on this size wire the WIRE is now the fuse, if there is a short the wire will heat up, melt and separate in the vehicle somewhere, fuse would be fine.
You want it to be the other way around.
So the fuse you use should be based on WIRE SIZE and then on the device being powered.
So look at the factory wiring size on the device to decide on what fuse to use.
The SMALLEST wire.
And you should use a slightly larger wire to feed that device, this is because of the distance from battery to device.
Wire ratings for 12volt
22awg => 8A
20awg => 10A
18awg => 15A
16awg => 19A
14awg => 25A
I believe heated seats should be 20amp if both are on the same circuit, or 15 amp if 2 wires and fuses are used.
Power seats would be about the same.
I think it is common to have power windows, power door locks and power seats all on the same 30 amp fuse.
Last edited by RonD; 01-03-2015 at 11:14 AM.