I just got 5 Hella 500FF lights (55W) and a Rugged Ridge light bar for my Jeep. I have the 2 passenger side lights to one relay and switch, the middle one to another one, and the 2 driver side on another relay and switch. My power for the switch is tapped into the AC fan motor under the glove compartment because it was easy to get to and only has juice when the key is on. My relay power was straight to the battery but is now to the fan blower too, I will explain why in a minute.

The individual lights are grounded to the bolts that hold them onto the tabs of the light bar. This worked as a good ground for about 30 seconds, then we dropped the bar all the way into its connectors and it stopped working. The bar is powder coated pretty heavily on the outside. Where it connects to the windshield brackets it has foam kind of stuff to protect the paint. I am thinking this is why the bolts up top can't be a solid ground. So I tested a longer ground wire from the far right (passenger side) bolt and ran it to a bolt on under the dash that is a known ground. This allowed all my lights to cut on. Great right? Well, no.

The wire I used to ground the lights is 16 AWG (I'm pretty sure). It is just leftover from the power cord that Hella has in the harness from the relay to the lights. When the lights stay on for about 1-2 minutes the fuses that are in-line from the relays to the power supply get really hot. The wires on either side or anywhere else are not hot. The ground wire itself gets very hot and actually heats up the light bar tubes where it drops down. I tried to move the power for the relays from the battery to the fan motor where the switches are drawing power thinking that the relays were getting to much amperage from the battery. This didn't help.

So finally to my question. The one ground wire must be the problem. It is pretty much grounding all five lights, again 55W each. I think that the ground wire is too small and building up too much resistance causing the wire and fuses to be hot. So do I get a bigger wire, if so how much bigger (12AWG, 10??) or do I take 5 of the 16AWG wires and run a ground from each light down to the bolt on the car.

Sorry for the long message but I want whoever can help me to know as much as they need first. But, as always, thanks for the great help and advice in advance.

 

That ground wire is only intended to be used for one light. And you are using it for 5. So yes, this is a problem. If you are going to continue to use the light bar for a ground? You will need to remove the paint / powder coat at each ground point. And you will need a #10 wire from the bar back to a solid ground in the engine bay.

 

Ok thanks. I am hoping it will work with just one wire because its a pain to fish wires through. Is there a way you knew it was #10 other than just expirence?

 

5 lites * 55 watts = 275 watts
275 watts / 12 volts = 22.91 Amps
20 Ampse = #12
> 20A and < 30A = #10

 

Ok thanks so much for your help.