Printable PDF VersionA mechanic of many years with his own shop brought in a froze up alternator on a 1992 Mercury Grand Marquis 4.6l. An easy
95 Amp 3G Alternator that we had sold him came back 40 minutes later installed on the car and not charging at all. The mechanic was very steamed that we sold him a bad alternator. We went out to the car and sure enough, the alternator wasn’t working at all. Unfortunately we thought he might have done actual damage to the regulator, since he said that after he installed it that he unhooked the battery cable from the battery and the engine died. This is a very wrong way to test alternators and can damage the regulator. But after removing the cap to the power supply box we could see the blown fuse for the alternator circuit. After replacing this, the alternator could activate and full voltage appeared. Since the first alternator was clearly bad, then it only made since that the replacement part was also bad and no further checking was needed. There are plenty examples that this is not the case.