so my 98 hatch is bone stock, no mods what so ever(daily driver). Anyways, the its hard to explain but I will try my best. The power seems to be lessening up and down, the lights dim and brighten, the heater blows softer and harder, all lights dim and return to normal on the dash. I thought it was my battery terminal or a wire loose, but everything is tight. Alternator is brand new, tested and runs fine. I cant seem to figure out what the problem is. It's obviously electrical, but what else can it be that makes all these things happen at once? It's really annoying and starting to get on my nerves. I would also like to add that the car did sit for a few years before I bought it.

 

Get the battery tested and see if its weak. I would even get the alternator checked even thou it is new. Everything you described sounds like a charging system issue.

 

You most likely are in need of a battery, transient loads on a battery with a poor state of health will cause a significant drop in system voltage until the PCM commands the alternator field up, which comes with a delay. If your terminals are questionable, replace them.

A bad battery will gas progressively faster and faster, which will overheat the alternator if the battery cannot store the charge, ruining the alternator.

The best performance upgrade for the dollar are battery terminals, electrical precision is extremely important.