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My alternator wobbles when the engine is running

Alternators

A visibly wobbling alternator will chew a belt and eventually throw it. Before assuming a bad part, work through the fasteners.

Overview

Short Answer

Confirm every bolt is torqued to spec, including the bolt that ties the bracket into the cylinder head. That one is the most often missed, and left loose it lets the whole alternator move.

Check the fasteners in this order

The bolt tying the bracket into the head. This is the one that gets missed. Your kit’s torque spec diagram calls it out.

The alternator mounting bolts at the bracket.

The alternator pulley nut itself. A loose pulley reads as wobble but is a different failure.

The back brace, if your kit includes one. That is the rod running from the top of the alternator to the head.

Everything in the accessory drive is load bearing, so all of it goes to the torque figures on your kit diagram, not to feel.

If everything is torqued and it still wobbles

Then you are looking at the alternator itself: a bent pulley, a failed bearing, or a pulley that is not seated square on the shaft. Take a short video with the engine at idle and send it to us with your order number. Movement is far easier to judge on video than in a still photo.

Don’t ignore it

Alternator wobble is one of the most common causes behind repeated thrown belts. If you have replaced more than one belt, start here. See also our article on belts that keep coming off.

Torque specs

Your kit ships with a labeled torque spec diagram. If you cannot find yours, email us your order number and we will send another copy.