Errs light comes on sometimes

Sounds like the generator is failing intermittently. All of the lights you listed are for systems run by computers, and those are very fussy about correct system voltage. When the generator fails, the entire electrical system runs on the battery alone, and that will run down in less than an hour.

Since the 1987 model year, GM has had a real lot of trouble with repeat failures of their generators caused by the huge voltage spikes they develop. The battery is the main component in damping and absorbing those spikes, but as they age and the lead flakes off the plates, they lose their ability to do that. To reduce the number of repeat generator failures, replace the battery at the same time unless it is less than about two years old. The old battery will work fine in an 1986 or older model.