Electrical Issues

97 Ranger XLT. My battery dash light illuminates intermittently. Had battery and alternator checked both checked out okay. Something is going on that's draining power because every time the battery light comes on, the lights get dim, signals barely work, dash lights get dim, heater fan decreases. any suggestions before I start changing parts

Check your ground cable for the battery at the starter end for corrosion or any damage.

Check your battery connections and grounds. A loose or corroded connection can cause all sorts of weird electrical gremlins. Also check the large wire going from the alternator to the battery. A bad connection there can cause similar issues.