ATC Auto Fuse selection table

Before doing anything else go here http://www.eatel.net/~amptech/elecdisc/fuses.htm

And read this page! It will give you the reasons for using a fuse!

*Device Amps*	*Part # to Use*	*Fuse Color*	*Rated Amps*
750 ma	ATC-1	Black	1
751 ma –1.5 amps	ATC-2	Grey	2
1.51 - 2.25 amps	ATC-3	Violet	3
2.26 - 3 amps	ATC-4	Pink	4
3.1 - 3.75 amps	ATC-5	Tan	5
3.76 - 5.625 amps	ATC-7.5	Brown	7.5
5.7 - 7.5 amps	ATC-10	Red	10
7.6 - 11.25 amps	ATC-15	Blue	15
11.3- 15 amps	ATC-20	Yellow	20
15.1 – 18.75 amps	ATC-25	Natural	25
18.76 - 22.5 amps	ATC-30	Green	30
22.6 – 30 amps	ATC-40	Amber	40

To use the chart find the current (amps) your device uses in the first column. Read the proper fuse size in the last column.

Finding the current or amps your device draws.

Current draw is usually stated in the product manual. If not you may have to call the company that made it. If you can’t find it then you have two choices. Find a friend or electrician with a VOM capable of reading current and take a measurement or use the trial and error method.)

Trial and Error

Make a guess as to how much current the device draws. Example: Hella 500 driving lights with 55 watt bulbs pull 4.9 amp EACH for a total of 9.8 amps say 10 amps. Note: Don’t confuse light wattage ratings with current draw! You CAN NOT always use the formula I=P/E where P = light watts! Light wattage ratings usually indicate lumens, a measure of brightness, not power consumed!

Using the table we see that the fuse to use is a 15 amp. Install the 15 amp fuse and try the lights. If the fuse blows and you know you don’t have a short then step up to a twenty amp fuse. If it still blows, you may have a problem with the wiring or the lights may have an internal short.

Here is a link for the mathematically and technically inclined!

http://www.e-insite.net/ednmag/archives/1996/092696/20df4.htm