That warning light means the charging system is not keeping the battery charged while you're driving. The generators on GM vehicles are a very high-failure item starting with 1987 models. Due to their design, they develop huge harmful voltage spikes that can damage the internal voltage regulator and diodes, and interfere with computer sensor signals. The battery is the key 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 high number of repeat failures, always replace the battery at the same time, unless it is less than about two years old. The old battery can still work okay in an '86 or older model.
Since you already replaced the battery, we don't have to worry about that, but the place to start is by having the charging system tested and repaired. The most logical suspect is the generator. If you want to start the testing yourself, here's links to some articles that may be of help:
You can find a perfectly fine digital voltmeter at places like Harbor Freight Tools, Walmart, or any hardware store or auto parts store for less than ten dollars. The voltmeter article shows using an auto-ranging meter which is a feature you don't need. If you have the less-expensive meter and need help selecting the ranges, I can help with that.
Tuesday, January 14th, 2020 AT 11:42 AM