Have you been suspecting that your Mercury alternator is slacking off on its important work? There are a number of ways to find out for sure. If the electrical power in your vehicle has been inconsistent, with lights dimming when you use the defrosters or windshield wipers, this could indicate a weak battery. If your battery is in good shape and fairly new, it may not be getting enough of a charge from the Mercury alternator. The first thing to check is the serpentine belt that turns the Mercury alternator for breakage. If the belt is in one piece, you should check for belt tension and wear. If the belt is not the problem, you should then check the connections of the Mercury alternator for corrosion, and be sure they are tight. If your problem is not in your connections, it is time to get the voltmeter. With the voltmeter set to DC, and the engine running at a fast idle, measure the voltage across the battery terminals. If your reading is less than twelve volts, you have an alternator problem. If your reading is good, try testing again with a few things turned on, like the lights and heater. If the voltmeter reads less than thirteen volts, the alternator will likely need replacing. The Mercury alternator is a relatively simple part to change, and not very expensive, especially if you choose your replacement from the selection of quality Mercury replacement parts in our online catalog at great prices. Our expert customer service can help you place your Mercury alternator order on our toll-free phone line, or it can be easily done yourself on our user- friendly secure site.