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The ground (black) terminal clamp on the battery in my 2007 Mazda-6 has become loose to the point that sometimes the start motor will drain the whole electrical system before it engages. At that point I have to pop the hood and shimmy the clamp to get a connection sufficient to start the car.

I have hit the limit tightening the clamp nut but I can still turn the clamp without much effort. (Maybe this is a consequence of differential metal shrinkage as temperatures have recently been below freezing?)

What is an expedient or proper fix for this? I don't see any corrosion on that terminal. My first inclination was to shim it with some copper wire between the clamp and the terminal, but for all I know that will cause galvanic corrosion.

Battery with loose black clamp

feetwet
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3 Answers3

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If the clamp is no longer getting tight enough, that could mean the metal is stretched and possibly weak. A dealership would want to replace the whole ground cable with a new, molded on clamp. If there is any slack in the cable, you can buy a replacement clamp and put that on the wire. One way or another, new clamp is the "proper" fix.

In the mean time, there are also "terminal shims" that are made to be a quick fix for this problem at many auto-parts stores:

enter image description here

Lead post shim, random example

They are made out of lead so you don't have to worry about different metals reacting with each other.

JPhi1618
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5

Replace it, with something like this:

enter image description here

Solar Mike
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2

My favorite is adding a "custom" shim...i.e. pounding a nail in there so it'll tighten up:

enter image description here

rogerdpack
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