As your GMC ages, so will the parts of the starting and charging systems. When your vehicle becomes hard to start in the morning, and the battery is known to be good, the culprit may be a partially failed GMC alternator. Anytime your vehicle is running, the GMC alternator provides the power to listen to the radio and turn on the dome lights. More importantly, it recharges the battery. If you suspect that it is failing, a voltage test is the first diagnostic routine to employ. With the engine running, the voltage at the battery should read just shy of 15 volts, if the GMC alternator is operating properly. Less than 14 volts may indicate a problem, at which point it may be wise to have the local shop do a load test, in order to double-check your findings and to take care of the problem before it leaves you on the side of the road. The GMC alternator has three independent circuits, and when one fails, it will show a drop in overall voltage. The other two circuits are sure to fail soon after, due to the increased current demand placed on them. When it becomes necessary to replace the GMC alternator, you will find the correct model for your vehicle in our vast online catalog, usually at a far lower price than what you would pay for the equivalent part from the dealership. Our version of the GMC alternator meets all of the highest industry standards, and comes with a full warranty from the manufacturer. With our quick shipping system, your new GMC alternator will be at your door in very little time.