Troubleshooting Checklist after a New Alternator Installation

A parked white car.

When you’re putting in a new alternator, there are a number of things you need to check after you’ve finished the installation. After taking the time to install the new alternator, you want to have everything set just right to be sure it works properly. These steps will ensure that you are able to get the best out of your new alternator and that it will last a long time. Carry them out and you’ll find that your car runs a great deal better than before.


Your battery should have been disconnected before you installed the new alternator. Make sure your car battery has the proper capacity for your vehicle and that it is fully charged. If the battery is defective in any way, your alternator will fail well before its time. If the battery is discharged, your alternator will only have a short life.

Wire and Cables

Check the battery cables and the wires to and from the alternator for any wear or corrosion. If the connections are loose, it will place more resistance on the entire electrical system which can damage the alternator. Make sure all the connections are tight before starting the engine.

Pulley and Fan

It’s important that the fan and pulley are in balance. If they’re not, they’ll create vibrations that could cause your new alternator to fail. Where the fan is damaged, the alternator won’t cool properly. If the pulley is damaged, the drive belts might slip and this will result in the alternator being driven at the wrong speeds.

If the rotor doesn’t spin freely when you unpack the alternator, go ahead and install the fan and pulley then torque the pulley unit; it needs to measure in at 70 to 80-foot pounds. After this, the rotor will turn freely in the alternator.


It’s important to use the proper hardware when installing a new alternator. You should always used grade 6 bolts with self-locking nuts and hardened flat washers. Don’t use lock washers at all. If the adjusting bracket is slotted, put a flat, hardened washer between the alternator adjusting ear and the adjusting bracket.


The alternator needs to achieve a certain speed for the regulator to kick in and for the field circuit to energize. If this doesn’t happen at idling speed, hold the gas pedal down until the regulator turns on. Once it’s activated, it will remain on until you turn off the engine.

Alternator Test

A new alternator should give an output that’s 20% more than the vehicle system requires and should have been set to this level during manufacture. Use test equipment to check the output of the charging system and ensure that it meets this level before driving regularly.