I recently installed a set of fog lights on my truck. When i wired it, i used a 6A fuse, which blew within a week. So i put a 10A in, and they ran fine, but the switch gets really hot to touch. Is this a short in the wiring, or just too big a fuse?? if so, what size should i use? thanks for any help

 

What wattage lamps are you running? If they are two 35 watt lamps, that would be 70w divided by 12 volts is equal to 5.83 amps. Although this is borderline for a 6 amp fuse, you must be running lamps that are higher wattage? If so, use the formula above, and figure out the amp draw. When you find out the amp draw, round up to the nearest one of these numbers:

10 amps
15 amps
20 amps
30 amps

When you find the amps that is nearest ABOVE your calculation, you need to size the fuse , wire , and switch accordingly.

10 amps=10amp fuse, 16 guage wire, 10 amp switch.

15 amps=15amp fuse, 14 guage wire, 15 amp switch.

20 amps=20 amp fuse. 12 guage wire, 30 amp relay.

30 amps=30 amp fuse, 10 guage wire, 30 amp relay.

I would recommend using the relay for the 15 amp circuit and above, mainly because 10 amp switches are easy to find, anything higher is more expensive and the relay is cheap.


Here's a diagram of how to hook a relay up. This is for high power back-up lamps, but would be the same for fog lamps too. Instead of hooking the one wire to the back-up light switch, hook that wire to your "fog lamps" dash switch. Then run power from an accessory source to the switch. This switch and power source can be very small, since the relay coil does not draw hardly any current.