The clock and dash lights get a lot dimmer once turning on the headlights. I've had this happen before when alternator was dying. Got a new one and dash lights and clock were back to being bright.

This time I drove to AutoZone and they tested the alternator and said it's fine, so I'm confused. If it's fine why are the dash lights dim again? Could this mean the alternator is gonna die soon?

 

Disconnect the battery and check to connections on the alternator. The nut that holds down the main cable on mine was loose so I was getting a poor connection. Also check when you connect the battery again if the battery is getting 14.5v with a mutimeter that will tell you if it’s at least charging the battery.

 

It could be the dimmer switch. My old one failed. I replaced it with a junkyard one. That later failed too. I now have it bypassed by simply jumping the wires together behind the switch. You can try pulling the switch out and connecting the two wires together to see if the lights return to full brightness.

 

I tested voltage on the battery recently with the car on, headlights on, and stereo on all at the same time and it was still showing 14.46v at the battery. Does that mean alternator is fine? I will test the bolt connection next.

 

So you had same issue as me? Clock and dash lights being dim when turning on headlights? Thanks for you input. If its just a dimmer switch it's not big deal for me, I'm just worried its the alternator.

 

Get one of those cheap cig lighter volt meters and check the voltage when driving.

 

Do the headlights and or dash lights / clock dim or blink upon brake pedal application? Any ground noises? If so, check the terminal connector on positive post. Look for broken or cracked battery post clamp , if you have oem style connector,check for corrosion also. My two pennys.

 

I started noticing that the headlights change brightness when braking while driving, but not when standing still. What is this a sign of? Bad alternator or connections? I cleaned the battery post and clamp as best I could and applied electric grease.

What are ground noises and what do they sound like? Are they heard on the stereo or where?