Home made alternator tester.
Here is an easy to make alternator tester. I used spare parts. You plug it into the cigarret lighter (I have relocated my cigarret lighter to under the dashboard).
The LED should be OFF when the alternator is not running.
The LED should be ON when the alternator is running, if the LED stays off your alternator is undercharging and is bad.
Note: this circuit will not test for overcharging alternators.
Here is the schematic.
Here are the componets.
Here is the final device.
Here the alt is off & the LED is off.
Here the alt is on & the LED is on.
