The Chevrolet S10 pickup truck series was manufactured with a 12-volt alternating generator system coupled to a single battery. The standard 105-amp alternator can provide sufficient electricity to charge the battery and run the truck while in operation, but can wear out and require replacement. The average backyard mechanic can troubleshoot the alternator of an S10 in about 20 minutes.
Take the alternator to a local auto parts store and have it tested. Most parts stores and some repair shops will test the alternator on a bench tool and check it for electrical issues. A normal alternator will put out over 14 volts, and if it drops to below 13 volts while "loaded," it has a bad voltage regulator, or internal wear, and must be rebuilt.
Listen for odd sounds that occur with the engine running from the location of the alternator. The Chevrolet S10 has a serpentine belt that winds its way through the various drive pulleys, including the alternator's. A sharp squealing sound could indicate a slipping belt, which would not spin the alternator and undercharge the system. A harsh grinding noise could be indicative of bad alternator bearings, at the center of the unit's pulley shaft. A loud humming or ticking sound, while rare, is caused by an electrical fault within the alternator's coils, which are dissipating the charge back into the truck. This is normally accompanied by "strobing" lights or random blown fuses.
Check the alternator's ground wire, attached to the engine block with a hex-head bolt, for a solid connection. This is often the most overlooked part of the system and can lead to most of the problems described above if left loose for too long. A shorted or weak ground can cause the truck's battery to slowly die, as it is not receiving the proper charge. The lack of a ground can also cause the alternator to short out. The S10 alternators have an internal voltage regulator, a sensitive electrical component, which can become damaged also.
