FLD Dash Gauge Lights NOT Working?

Have searched here and elsewhere online but nothing has solved my issue. Hoping someone here can help. I've replaced all of my relays with brand new ones and have totally cleaned up the circuit breaker block. I've also put in a new circuit breaker, headlight switch, and dimmer rheostat (relay) yet only two or three dash lights work and occasionally flicker. Anyone have any input or know where the grounds might be that run to the breaker box? Thank You!

 

Okay, I'll go through these tests today and report back with what I find. Thanks for the replies!

 

Thanks! So, the emblem lights don't work at all and haven't since I've had it. The gauge lights are the ones that are flickering and some are not on at all. I've installed a brand new headlight switch and new dimmer switch, both from the dealer. Bought an extra headlight switch just in case. I've also installed all new relays under the dash.

I'm chasing grounds right now, but didn't know where the dash ground contacts the frame or where it exits from the dash. The schematic on the door shows white wire 29A from the dimmer branching off to both the tachometer and a ground. No idea where that ground is.

I've completely changed the ground wire that attaches cab to frame at the left steer tire area. I have checked the ground at the drivers side rear of sleeper. There isn't anything attached to the passenger rear sleeper ground post.

I went to remove the ground, for what I assume would be the headlights, from the post at the right steer tire by the fan, but that nut and threads are so corroded, it snapped off of the frame. Made no difference to the dash lights, so guess that wasn't it. Luckily there's another ground post close to the now-broken one I can put those eyelets back onto.

Just about at a loss. What would the adjuster switch be?

 

Welp, I just found the issue, and BOY do I feel like a REAL dumb ###. So, I bought these blue 1895 LED lights a couple years ago when we bought the truck. Worked great when I put them in. Over a few months time, they would start flickering and dim out to nothing, one by one.

I found this video on Youtube tonight of a guy changing his LED bulbs. He happened to mention that sometimes they go out, and I thought SURELY my LED bulbs haven't burned out! Because they're LED's, right?? And they're basically still new..!

I took the one working bulb and swapped it into another plug and I'll be ######!! The sockets work just fine!! Swapped a bad bulb into the socket that had the working light, and sure enough, the bulb was just bad.

I guess my lesson from this is, sure, check all the things anyway, clean the corrosion, install new parts that were old, and put on some new grounds. But also, check the #### BULBS. Geeezus, two years...

Thank you all so much for the help and insight. I really did learn more from your all's advice here about troubleshooting some electrical issues on my truck.