Hi everyone, this is my first post here, so sorry if I make any mistakes.

I've got a 2000 Blazer 4-Door 4WD that I'm trying to restore and make roadworthy once again (it was a plow truck for several years before now), it's got several issues, but the biggest issue (and the one I'm fixing first) is one with the interior electronics. As the title explains, the dash, radio and dome lights will only work with the high beams turned on (headlight switch turned on, turn signal stick pulled back for high beams). When the interior electronics are on, pressing the door lock switch causes everything to flicker. After a while of having the electronics on and leaving them on, everything will start to flicker in a similar manner, just more slowly. The low beams also don't work. I think both these issues are related.

I've tried cleaning both grounds on the radiator core supports, and also the ground on the driver's side firewall, and those haven't resolved anything. After that, I thought it was the body control module, so I put a new one of those in, and that didn't help it either (it actually caused it to not start because it wasn't programmed to this Blazer, lol. It should've at least enabled the interior electronics if it was to blame, however). So now I'm thinking that it's either another ground somewhere else on the frame (possibly below the interior), or it may be a relay somewhere that failed.

I'm honestly at a loss, so if anyone has had a similar situation and/or has any light to shed on the issue, I'd greatly appreciate it. If a picture/video of the issue is necessary, I can take as many as needed.

 

Welcome to the forum. You mentioned that it was a plow truck so I'm assuming the plow has been removed. Because the plow blocks the factory lighting many plow trucks have remote high-mounted headlight/turn signal assemblies. If those were removed and the wiring wasn't returned to stock correctly it could cause the problem you're experiencing.

 

The plow setup hasn't been removed, the light (there's only one, and no turn signals), frame, and pump are still on there, just without the actual plow. My reasoning for that is that in case the main plow truck (a 1996 Dodge Ram 2500 for anyone curious) dies unexpectedly, it's useful to have a spare. The frame without the plow doesn't block the stock headlights or turn signals, so I figure it's okay to drive with the frame on. The wiring for the plow runs directly to the battery, separately from any of the stock circuits or grounds, so the stock headlight circuit should be unchanged. The switches are mounted to the plastic trimpiece/tray that goes around the cassette deck, in front of the cupholders.

Reading up on similar issues, I've heard of there being more grounds, one on the frame right around where the B pillar is on the driver's or passenger's side (not certain), and another somewhere around the fuel tank. Tomorrow I'll more than likely be getting the truck up on ramps to see if I can spot any more grounds. If you or anyone can point out any specific ground locations (there was a diagram of them somewhere in the electrical section of this forum, but they weren't all too clear), it'd speed up my troubleshooting.

Thank you for your help.