Having things like the lights go out but the engine still run could mean that there is a intermittent fault with the ACC contacts of the ignition switch or possibly a relay if there is one in the circuit for the vehicle accessories. You should really consider getting a factory service manual at least for the wiring of the car. It really helps you pin down where areas of trouble could be when you use the clues to the trouble. Ebay is a good place to get manuals for a reasonable price.
Did your battery fail a load test OP? Is that why you replaced it, or were you hoping that would fix it and took a shot? Replacing the battery was just a guess in other words? No worries, at least you know you have a good battery.
If I had the problem of the dash lights and headlights dimming noticeably at idle but getting bright as normal with increased rpm, my first suspicioun would be an alternator on the fritz. Next up would be a problem with the wiring between the alternator and the battery. For example if both the alternator and battery are not properly grounded with a low resistance path to the chassis, that symptom could result.
The first test I’d make is when this dimming thing is happening, measure the voltage at the battery posts, and again at the battery connectors. And compare those readings to the same readings when you bump the rpm and the dimming no longer is occurring. You are welcome to post your results here.
So I found out what the problem was. It was kind of stupid on my part. When I replaced the alternator apparently I didn’t screw the wire going from the alternator to battery tight enough. I had a guy look at it for me and he started banging on the alternator and when he did sparks started flying. Like I said though stupid on my part but I’m learning. Never really worked on cars much. Thank you guys for your help.
You’re welcome for the help and glad you found the problem. The main output lead of the alternator has to handle a lot of current to supply power to the battery. Any small amount of resistance due to a loose or dirty connection can result in a voltage drop across that resistance. That usually means the connection gets hot and a lot of the time damages the connection. We all have learning experiences like this we could tell about. The good thing is you will most likely never make that mistake again.
Thanks for posting the result OP. Good to know we were able to help out. And no worries, even the mechanics who build the cars at the manufacturing plants – new – don’t always tighten the fasteners to the correct specs. Ask me how I know this … lol …
Well some years ago I had replaced an alternator in my Olds in cold Winter. A couple days later the wife was at the grocery store and the battery was dead. After picking her up I bought a new battery and proceeded to install it in the car when I realized I had failed to plug the alternator in. Well I got a new battery out of it anyway and rescued a damsel in distress. We usually only do these things once and don’t talk much about them. (This was a special order Olds that I ordered the gauge package so it had a volt meter and no battery light. Guess I didn’t look at it.)