If a jump start fails to charge the battery and start the engine, it is an indication that the alternator is at fault. To test this further, With the engine running, touch the positive probe on the multi meter to the positive terminal on the alternator. Then touch the negative probe on the car’s frame or a bolt head. It should show a reading on your multi meter of around 14 volts. If the reading is higher (15 volts or greater), this indicates a fault in the alternator and may soon fail. If the reading is below 13 volts, it may be a case that the engine’s idle speed is too low for it to charge the battery. By revving the engine, this increases overall engine speed which usually solves the issue. If not, you may have a slipping belt or a regulator that needs replacing. For more information on alternators,
see our guide
