20" Light Bar keeps blowing fuse...

[Verruckt]

I know this should be simple, but for some reason a new 20" light bar I'm installing on AUX 2 keeps blowing my 30A fuse, and I'm stumped as to what it could be.

I've disconnected the light bar and checked voltage across the connector on the harness in the vehicle and I get the proper 12V when flipping the AUX 2 switch. This doesn't blow the fuse.

I've put 12V from a battery to the light bar with a test harness that has a 30A fuse, and I have no problem - it lights up and doesn't blow the fuse in my test harness.

However, for some reason, when I connect the light bar back to the harness in the truck, and flip AUX 2, it blows the fuse every time. It's almost like the fuse won't blow when I meter it, but once the load of the light goes on it, it blows.

I thought it could have been bad wiring of the pass through wires, but my voltage checks out no problem. Any ideas from those who have done this before / encountered these issues before? Thanks in advance!

 

[IRONMAN]

I know this should be simple, but for some reason a new 20" light bar I'm installing on AUX 2 keeps blowing my 30A fuse, and I'm stumped as to what it could be.

I've disconnected the light bar and checked voltage across the connector on the harness in the vehicle and I get the proper 12V when flipping the AUX 2 switch. This doesn't blow the fuse.

I've put 12V from a battery to the light bar with a test harness that has a 30A fuse, and I have no problem - it lights up and doesn't blow the fuse in my test harness.

However, for some reason, when I connect the light bar back to the harness in the truck, and flip AUX 2, it blows the fuse every time. It's almost like the fuse won't blow when I meter it, but once the load of the light goes on it, it blows.

I thought it could have been bad wiring of the pass through wires, but my voltage checks out no problem. Any ideas from those who have done this before / encountered these issues before? Thanks in advance!

Well the only thing I can think of is a short somewhere. Did you try and plug some other light or 12v something by chance to that Aux switch to see if it'll blow.
You could also just use that Aux switch to trigger an external relay and fuse and wire it directly to the battery if you know what I mean.
I've done that for 2 light bars off the same Aux, a 30" and 40"

 

[The Car Stereo Company]

yeah, something is not right. recheck all the wiring as far as you can to make sure everything is correct. i have heard of a select few people with bad aux switches/wiring harness so that may be your cause

 

[Verruckt]

Welp, figured it out. The short of it (heh) is the light was grounding out internally to the light body and flowing to ground through the mounts.

Putting this here in case anyone has the same problem / needs help with diag steps I performed (a little long):

1: Checked the harness from the switch to the light by putting a meter on the positive side of the light harness (connector between harness and light), and verifying I had 12V still. Also checked resistance to ground with the switch OFF and was OL to ground - so no shorts to ground on the positive side, and good voltage. Also did a wiggle test on my connections and none of this changed.

2: Checked the harness from the switch to the relay. Did this by putting my positive probe in pin 5 of the AUX 2 relay (Same color wire as in pass thru area - GN / BN), and then my negative probe on a ground point - No resistance again, so therefore no short on this path / harness.

3: Checked the entire harness from relay to light plug. Basically the same as above, pin 5 to the ground of the plug. With the switch off it should read OL ad there's no path to complete the circuit. With the switch on it should read 0, meaning a good circuit. So no short / path to ground there either.

4: Tested light out of vehicle, connected to harness, on top of the bumper. It worked. Wiggled wires and no cutouts at all, so my connections were good.

5: Figured out the body of the light must be grounding out through the mounts. Sure enough, from the positive side of the light plug, to the body of the light, in a slightly scratched area, I was getting continuity. Something internal must be shorted to the body.

I called the vendor, and they're sending me a new light.

On a side note, I think I know how to wire these easier now. Posted the gist of it in the Aux wiring how to thread. I took some pics throughout my diag and will post more info later today / tomorrow, but you shouldn't need to deal with this stupid pass thru area anymore to wire up lights to your aux switches.