My SPEEDWAY headlight switch also operates taillights and gauge lights is it okay to operate all of those lights off a single 25 amp fuse? If not, how do I separate taillights and gauge lights for their own fuses?
How many contacts and terminals does the switch have? Most light switches have separate contacts/terminals for at least the headlights and taillights, if the switch has those simply run incoming power from the fuses to the respective places. If not, you can run one power wire to the switch, then fuse the taillights and dash lights after the switch. I'll also comment that you should size the fuse to the load. Add up the wattage of each lamp in each circuit, total that, then divide by 12. This gives amps load, then size the fuse at 125% of the load. If you end up 'between' sizes, it's ok to go up to the next size.
Here's where I get confused Steve, I already have power coming to the the switch from the fuse panel that has a 25 amp fuse; so I can run the gauge lights from fuse panel to the terminal on headlight switch that is for gauges & taillights? Seems like I'm running power to the same terminal twice, once throughout the switch and once through the fuse panel.
Not knowing what a Speedway switch or schematic looks like, all I can do is explain what to look for on the switch. First, how many positions does it have? Is it just on/off, or does it have off/park lights/headlights positions? How many connection terminals does it have? If it's a simple on/off, one terminal will be power, and if it only has two total, the other will be for all the lights. Any additional terminals will be for separating the additional lights. Three position switch? Then it can get complicated; depending on the number of terminals, you may have only one power connection or you may have two or three. This can be checked with an ohmmeter. With the switch on the bench, check for continuity between the terminals when it's 'off'. If you get continuity between any terminals, these are 'common' and will have power when the other side of the switch is closed. These will almost surely be the park and tail terminals if there's two, but could be dash and tail. Now move the switch to the 'park' position. You'll have continuity between a power terminal and the dash/taillights terminal. If you have only one terminal left, that's the headlights. If there's two left, one should be headlight power and the other headlights. With the switch pulled fully on, if you read continuity between all terminals, the switch has only one power terminal. If you have continuity between sets of terminals, i.e terminals 1, 2, and 3 read together and 4 and 5 do too, but not between 'sets' i.e. 4 and 5 don't read to 1, 2, or 3, you have two power terminals. And no, you don't want to run two supply wires to the same terminal...
Ahhh, your pic just showed up.... Simple; you only have one power terminal, only one wire should connect to it. The fuse in this wire should be sized for all of the lights, if you want to fuse the tail/dash lights you'll need to use an inline fuse after leaving the switch.
You could use the switch to energize relays for your headlights. Then you could fuse a separate circuit for head light power. Then there would be less amperage going through the switch.
That's really only an issue if the switch isn't rated for the load or you're really close to it's max rating.
Okay, that makes it simple, gauge, taillights & headlights run off one fuse. Thanks for clarifying things for me.
I will make a suggestion for safety; rather than use a fuse, install a correctly-sized circuit breaker instead, then install an inline fuse to protect the tail/dash lights. This way, if you do get a short in the tail/dash lights, you won't lose your headlights too. The breaker won't trip if just the fuse blows, and if you have a short in the headlights the breaker will 'cycle' (reset) and maybe get you home before you run out of fuses....
This is the first headlight switch that had both high and low beam terminals. Usually there is only one and that feeds the dimmer switch. Also, the headlight switches I know of have a built in circuit breaker that will cycle if there is a short in the HEADLIGHT circuit. The idea of putting a fuse inline (or in an isolated fuse on the fuse panel) in the tailight circuit is a good one as you will not affect the headlights.
Look here: http://www.jalopyjournal.com/forum/showthread.php?t=843579&page=4 ... posts 61 and 64 will explain this.
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