My head lights and dash lights dim and brighten while driving. Seems to be more spastic when accelerating. What do you guys think. Would hate to have to trace a bad ground.

 

If you have a powerful aftermarket audio system, it could be that.

 

No aftermarket audio.

 

Bad ground was my first thought. Maybe your alternator is going or the pully/belt is slipping.

 

Yah. Alternator. All your power comes from there. Could still be just a bad ground somewhere, though. How many miles do you have on it? Do you drive in harsh environments? Very cold, very hot? All those could help point to failing alternator.

 

It has 180k miles. I live in Florida so more hot than anything. What would be the place to start or way to go about testing for bad ground?

 

The circuit with the symptom, lighting, is the place to start.

It's easy to diagnose an alternator though. So you're in Florida, where you have both heat and humidity, and both of those shorten the life of the alternator. Are you the original owner? Back in the old days, when we used dinosaurs to power our trucks, we would be lucky to get 60-80k out of an alt (in heat and wet) before one of the diodes failed and caused symptoms like you describe. Rebuilding sometimes replaced the winding and always replaced all the diodes, making it as good as new.