How to Adjust an Alternator Belt Tensioner

Written by stephen benham | 13/05/2017
How to Adjust an Alternator Belt Tensioner
Adjusting the tension of your car's alternator belt constitutes a moderately easy process. (New car petrol engines image by Christopher Dodge from

Your car's alternator belt will stretch over time; eventually, it will start to slip. This condition can mean your alternator is not producing the right amount of electricity to power your car's electrical equipment and, more importantly, your car battery will not charge sufficiently. Your alternator attaches to the engine via three bolts; two are fixed, and the third is attached to an adjustable bracket. If your alternator belt has come loose, you must adjust its tension. The task is straightforward, although some alternators are located in places you'll find difficult to access.

Remove the positive battery cable from your car battery with a wrench. Move safely out of the way of the battery terminal.

Locate the three bolts on your alternator. Two bolts connect your alternator to the car engine: one at the front and one at the back of the alternator. The third attaches to an adjustable bracket.

Loosen both bolts that connect the alternator to the engine using a wrench. You may need to use two wrenches: one to hold the nut and the other to unscrew the bolts slightly.

Loosen the bolt attached to the alternator and the adjustable bracket. Place one wrench behind the bracket to hold the nut, then place the other wrench on the bolt on the front of the bracket. Turn the wrench counterclockwise to undo the nut and bolt slightly. The alternator should now move.

Use one hand to pull the alternator away from the engine. This action will adjust the belt's tension. Pull as hard as you can, then use your other hand to tighten the bolt clockwise. Check to ensure that the alternator and belt are tight. Tighten the bolt on the adjustable bracket using the two wrenches.

Tighten the two bolts that connect the alternator to your engine. Check all three bolts again to ensure that no movement occurs. Recheck the belt to check its tension.

Reconnect the positive battery cable to the positive terminal of your car battery.

Things you need

  • Two wrenches

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