Step 6: Testing
Set it to volts DC and connect the probes to the live (yellow on red) and earth (black) wires. You should get a reading of battery voltage (around 12.5 volts or so).
Start the engine. The voltage should stay around the battery voltage of around 12.5 volts at idle. Turning on the sidelights or the brake light should make it drop to around 11 volts. Increasing the revs should make the voltage increase to over 13 volts but not more than 15 volts.
The ammeter on the dash should be sitting in the green at idle and should go slightly more positive when the revs are increased.
If you see over 15 volts, Shut it down immediately. That means it's not regulating the voltage and could burn something out. Check your connections, especially the earth. If it's still doing it, chances are the regulator rectifier unit is faulty.
If you fail to see 13 to 14 volts when the engine is revved or the ammeter stays at zero or in the negative, it is not charging. Check the alternator output by disconnecting the two violet wires and measuring volts A.C. between them. It should go up to around 30 volts when the engine is revved. If it fails to do so, your problem is elsewhere. If it does, double check your connections then suspect a faulty regulator rectifier.
Here's a video of me testing my one: