Voltmeter Test
WARNING: This page is about a different car, the 1994 Chevrolet Caprice. However, it is still accessible from the selected car via links, so may be relevant.
Turn ignition on. Install voltmeter between battery terminals and note reading. If voltmeter reading on vehicle differs from battery voltage reading, ensure wiring to voltmeter is okay and connections are tight. If connections and wiring are okay, replace voltmeter or IPC.