How to Fix a Bad Car or Truck Battery Terminal Connection

A bad or loose battery terminal connection can cause a lot of different problems such as, a slow or intermittent engine start, and dim headlights The real problem with late model cars and trucks is the constant voltage requirement for all the computers and electronics. If it turns out that the battery is good, it might also be the alternator but, that’s another subject.

A battery cable end connector should not move at all if you wiggle it and it is properly tightened to the battery post terminal. The connection should be solid but, that’s not all. To begin your investigation, start by removing the battery box cover and check the grounding system of the car, this will be the negative – terminal and the ground cable and disconnect it. Always disconnect the negative first and reconnect it last. Corrosion and oxidation are two of the biggest reasons for a poor connection therefore, this is the first and, most obvious, place to start. You need to clean the terminal posts and the cable end connectors both mechanically and chemically. Grab a piece of sandpaper the size of a credit card and fold it in half and wrap it around the battery post and twist it around, just as you would when you’re tuning the radio. There is also a special wire brush tool with internal brushes for cleaning the post and a round brush end for cleaning the inside of the cable end connector. Use these to clean both parts until they are shinny bright metal. At this point you can use a baking soda paste, made with baking soda and water, to polish the post and terminal and wipe it off with a damp rag.   Now connect the positive terminal first and the negative last. If this doesn’t solve the problem, it’s on to the next.


All batteries use connectors with terminal fittings that rely on nuts and bolts to apply the force to make solid electrically sound connections.  Therefore, make sure the fasteners are tight so that there is no movement when the cables are wiggled. Keep in mind, these are small nuts and screws, so do not tightened to the point where you break them. If this solves your problem, you’re good to go, if not, on to the next.


The last issue is a damaged top post battery terminal. This can happen because of a loose connection causing arcing or oxidation and consequent degradation. The remedy for this is a solid lead battery terminal insert or, as commonly called, a battery terminal shim. This item looks like a thimble with a skirt and it is made from a thin piece of pure lead so that it can mold itself to the post and cable end connector and provide maximum conductivity. These are made by several companies such as Delco, Schumacher, Ucell, and Tech Team. Tech Team’s #809 set of 8 solid lead shims is highly rated and is the best quality and value  You can do a hey Siri or hey Alexa Google search for other options or watch the you tube video  as this will give you a good idea as to how they work.