I am wiring 4 100 watt lights to my roof. i wired one set but only one comes on and its dim... i grounded lights and switch under the hood... are my grounds too long? or what else should i check... im not using a relay as my switches are rated for double what my lights draw..

 

Do you have all the lights coming to two wires coming down from the lights on the roof? If so then you need to make sure that the wire is pretty thick.. Same for all the other wires for that matter.

 

And make sure that the ground has no paint or anything and that all the wire connections are strong. Probably a good idea to have an in line fuse in there somewhere too.

 

For each pair i ran a separate power wire .. i installed inline fses all ground wires are under the hood. can i run the grounds direct to the negative on batery

 

The longer your wires are the greater the resistance will be, keep your grounds short and using relays will vastly improve the output of your lights.

 

x2!!! Make sure your ground wires are making good metal to metal contact.

 

So what do relays do... i thought they just lighten the load on the switch.... also i have nowhere to ground them unless possibly drilling into roof... i have pics but cant figure out how to post them... i can send pics thru email if someone wants to see what im working with.. thanks

 

Do a little poking around on this site too. Don't just run lights off of a switch. You want it run through the relay set up for best results. http://www.the12volt.com/installbay/...asp~FID~5~PN~1

 

Yea the relay takes the load off the switch. I have 4 lights on my roof rack as well and have all the grounds in the engine bay. I'd double check the grounds, connections between wires, and maybe how big the fuse is.

 

 

A schematic, now we're in business.

 

Thanks for the input and diagram... i found the second lights failed because of loose pwr wire.. now one light is kinda bright but when i attach the ground on second one it lights up but both very dim.. would a relay fix this or what are my other options.... still havent even got the second pair wired yet

 

Good schematic...since you have 4 just do this twice. I agree the relay makes life easier.....I have a fuse inbetween my relay and battery..if you don't have an "indicator" like the schematic just leave that part out

 

Thank you all for the advice... i beefed up my power wires added a relay and the first set works great

 

If your pumpin 100W per light, u will need 10ga feed wire to be sure. Use a heavy, 10ga, ground wire too! Length not relevant unless your going thru a 500 ft roll before termination. Remember P=EI, (Watts= Volts x Amps) At 100W and 12Volts, your going to feed 8.4 amps per light. You should run 2 relays and 2 supply wires. I also run dual ground wires, in case one fails (corrosion, tree branch snag, etc.) Your switch cant feed that kind of amps. Solder connections where you can.
Some pics?