Aux Lights Went Out

Hi all,

I have my truck setup with a light bar, ditch lights and rear lights, all of which went out on me today. I last drove the truck on Friday (Dec 23rd) and we had some cold weather after but it cranked up fine today when I drove to the store.

From battery, wired to a Bussmann 100 Amp Circuit Breaker then to a Blue Sea Fuse Block, from there the rear lights are connected to the block with in-line relay and the light bar/ditch lights go to their respective relays and two-way diodes which allows me to flip on both lights with either my high beam toggle in the cab or two individual switches in the cab (fuse taps used for the high beam toggle as a signal).

First thoughts were mice, but I pulled the fuse block/breaker mounting plate up and no visible damage. Interesting thing I noticed, if I hit a toggle for any of the switches the led backlights on all the other aux switches for the aforementioned lights go out completely. No issues with the rest of the truck or my regular high beams, headlights, or fog lights.

My plan is to pull it all apart as soon as I have time and replace connections, clean everything, and slowly add pieces back in. No blown fuses that I can see and although there's a bit of rust, dirt, and corrosion in areas, nothing major. Battery is a few years old but not my primary suspect since the truck is starting and running fine after multiple cycles today.

Any ideas based on the above?

 

Well could be a lot of things. The fact that the lights in the switches don't turn on suggest a short somewhere in the line. Start with the easy first. Sometimes a fuse can look good but is blown. Replace that. Then check the ground, make sure it's all good and free of corrosion. Then the same for the hot wire. If none of this works time to try other common points. Bypass the circuit breaker, see if it works now. Change out or bypass the relay. Just work your way thru the circuit until you find the problem. And then if nothing works, check your fuse again because something in the line could be repeatedly blowing fuses.

 

Yep it's a bit overwhelming...so far I've verified the rear lights have no issues but I'm still messing with the ditch and bar harnesses. Something I noticed in the relay wiring, the way the ditch lights are currently wired up the 87 goes to the battery and the 30 goes to the lights. Most diagrams show it the opposite way, not to say that's it because the lights have worked fine for five years now but so far that's the only thing I've caught out of whack. I am replacing all the connections though, just trying to do it in a way that I can test the relays as I do.

 

This is the relay that came with the harness, from caliraised I believe.