I've been trying to wire lights in my side tool box which is part of my truck cap. The lights are two 55w halogen lights. I've run 10awg wire from the battery to the tool box and I have a switch rated to 25 amp. I have a inline 15amp fuse which I think should be sufficient. I have a ground running off the switch and a grounds running off each light. The power off the switch runs to the two lights. Every time I hook everything up, connect the battery and flip the switch the fuse blows. If my equation and math are correct my lights should only be pulling about 9 amps. I'm at a lose of what I'm doing wrong. I have good connections and wire protection loom covering every bit of the wire so there are no shorts. Any of you electric smart?

 

I would try removing one of the 55w bulbs and see what happens, if you haven't already tried that.

 

You're running a switch without a relay? You ground a relay but normally you do not ground an unlighted switch. It sounds like your ground off the switch is a short circuit which is overloading your fuse. Go to the parts store, buy an ice-cube relay and wire the circuit up correctly

Like this:
http://www.rallylights.com/hella/AuxLampWiring.aspx

 

Adrianspeeder

 

Just curious: why are you switching the relay ground (pin 85) instead of the control (pin 86). It will work either way but I've never seen it done that way.

Also, in a lot of cases I'd want the control pin to be wired to a source that's hot in run rather than hot at all times. That way turning off the ignition kills the lights. Too much chance of leaving something switched on, although there's less chance of that with work lights.

 

Thanks for the replies. I finally got around to going over the wiring and lights again. The lights are made to be outside so they had a rubber seal over where the wiring connected to them. I pulled the rubber back and realized I had the wiring backwards.

To answer a previous question, the switch lights up when turned on which is why its grounded. The switch is rated for 25 amps and I have a 20 amp fuse inline so I think I should be good to go without a relay. Is there another reason to have a relay?

Thanks again to all who replied. The lights work awesome.

 

If the switch can actually handle the lights' current, and you don't want to interlink the circuit with another, there's no need for a relay.

 

Well like you said it works either way, and that was prolly the way I did it first, and I stay consistent.

Adrianspeeder

 

Yep, it's been my experience that if the lights are too much for the switch it will fry the switch without a relay, usually not blow the inline fuse. For that much light I would probably still use a relay to be on the safe side. My luck the stupid switch would blow when I needed the lights most.