Headlamp and dash lights flickering/dimming

I have a 1995 Buick Regal 3.8L V6. I have a couple of problems with the car at the moment and one that is puzzling me.

1. Rear brake lights don't work unless I fiddle with signal switch (Problem is the switch I'm pretty sure). I mention it because problem #2 is also an electrical issue.

2. Both the headlamps and the dashboard lights flicker a lot. It's more like they dim and then regain their strength repeatedly. In addition, on the left side of the dashboard, the light intensity is not as bright, so I thought it was a bulb issue, until that side brightened up on me one day (but most of the time it stays dim).

Any ideas?

I've had the headlight flickering issue as well. I have a '94 Regal and there is a fuse block under the hood on the drivers side. I had a bad connection where the battery cable plugs on to the fuse block. It was actually sparking and melting the red protective plastic cover. I just unscrewed the battery cable from the fuse block, sanded the terminals, and put some dielectric grease on the terminal and screwed it back on. This got rid of the headlights flickering and my ABS light from coming on. I still have an occasional flickering in the instrument panel but I figured it was a loose light bulb or something.

Also, check all your battery cables and clean them if needed, then check alt output and regulator at AutoZone or Advanced.