Assuming you would like a step-by-step guide on how to check an alternator on a 2010 Jeep Wrangler: 1. Park your Jeep Wrangler in a safe and level area. Turn the engine off and pop the hood. 2. Disconnect the negative battery cable from the terminal using a socket wrench. This will prevent any electrical shorts while you're working on the Jeep. 3. Loosen the bolt that secures the alternator's positive battery cable to the terminal using a socket wrench, then remove the cable. 4. Unbolt the two (or three, depending on your model) bolts that hold the alternator in place with a socket wrench, then carefully remove it from the engine compartment taking care not to damage any of the surrounding wires or hoses. 5. Inspect your old alternator for any obvious signs of damage such as cracks, burns or missing parts; if it looks damaged beyond repair, replace it with a new one following Steps 6-9 below. Otherwise, proceed to Step 6 to have it tested at an auto parts store or by a professional mechanic before reinstalling it back in your Jeep Wrangler. 6. Bring your old alternator to an auto parts store or have a professional mechanic test its output using an electronic Alternator Test Bench (ATB). If it tests bad, replace it with a new one following Steps 7-9 below; if it tests good, skip ahead to Step 10 to reinstall it back into your Jeep Wrangler . . . but keep in mind that just because an ATB says an alternator is good doesn't necessarily mean there isn't some underlying issue causing premature failure so you may want to err on the side of caution and get a new one anyway (see Step 8 below).