Battery warning light
I have a 1999 Mustang GT and have the battery warning light coming on and off intermittently for the past 3 months or so.
Alternator was replaced 2 years ago and battery less than 1 year ago.
Car starts up and drives just fine and never had any issues until today.
This morning when I went to put the key into the run position, I noticed that all the analog dials swept to the max position and back to zero. Car starts up just fine. I drove it about 1-2 miles and parked.
Came back to the car, key into run position and the dials swept through again. But when I tried to start, the starter clicked and loss all power to the car. No dome lights, no trunk lights, nothing. Like there wasn't a battery in the car.
Popped the hood, and disconnected the negative cable from the battery. I reconnected the negative cable to the battery and the power came back on in the car. Key back in run position, dials sweep and car starts up just fine.
Drove another 1-2 miles and parked for about an hour. Went back to car, key in run position, dials do not sweep and starts up just fine. Drove 3-4 miles and the battery warning light came on for a bit, then went away and came back on again.
From my Google search, I found a lot of people saying to "check the grounds". I really don't know what that means.
Any ideas? Help! Thanks a bunch.
1999 GT Dark Green Satin