Where can I get an accurate voltage reading of what is truly flowing through the car? A tech told me that my voltmeter was inaccurate, but I'm just not convinced. When I start the car cold, there is plenty of voltage according to the voltmeter. But, once the car gets hot and the fans kick on, the voltage will linger around 13v or slightly less. When I have the lights on the voltage will suffer more. I notice the power loss when I'm stopped, and everything slows down. I have looked for a bad wire or some exposed wiring, but I don't see anything like that at all! So, where can i go to get a proper reading of what's going through the system? The car is an '89 IROC L98 Auto. I put a 140 amp alternator in the car to remedy the situation, but no change.

 

The best place is at the battery.
On my car, I have found that the cigrette lighter socket voltage is very close to the actuall battery voltage (it dose not go thru the ignition switch). I have a small digital volt meter that I plug into the lighter socket. I just ignore the inacurate dash gauge.

 

Get a digital voltmeter and measure directly across the battery. Chances are you will find a significant difference between it and the guage.