Testing a car battery is done prior to checking the alternator. Learn how to check a car battery before replacing or rebuilding an alternator in these free auto repair video instructions featuring a certified mechanic.
In this clip we're going to talk about the proper service procedure to remove, inspect and overhaul your vehicles alternator. In this step we're going to talk about the proper service procedure to check the vehicles wiring and insure that's not the trouble with our alternator. We're also going to be unhooking our negative battery terminal, once we're done verifying our wiring. What I'm going to do from here is my heavy duty test light and hook it up right there on the nice, clean, negative post. From here, I'm going to go ahead and take and jab through the battery charge line. Now, there's a reason why this line has a rubber cap on it. This runs directly to the battery and is hot, even when your engine is not running and the alternator does not have power to it. What we're going to do is establish the integrity of that circuit. As you can see, I just pushed through the rubber insulation and made contact with the terminal stud and have a lit ball. What that does, is indicate we have good flow through that portion of the charging system. From here I'm going to go ahead and take and test the two wires on the voltage regulator, that are command wires. One's going to light up real bright, the other one is going to light up pretty dim. We have three terminals here, I'm only checking these two cause their the ones that are important. This terminal here should light up for us. Now, that's with the key in the run position and this terminal here, as I said, it will be kind of dim. Once we verify the integrity of those three wires, we can be sure that our failure is inside the alternator. What I'm going to do now, is going ahead and unhook my negative battery terminal. You're always going to want to unhook the negative battery terminal before servicing any components on this. You're going avoid electrical shock and potential fire hazards. I'm going to go ahead and grab my thirteen millimeter and take it loose. And, you want to twist it off, just like so. You're going to want to make sure that you tuck this away in a location where it will not contact the negative battery post. That is the proper way to inspect your wiring on your alternator and unhook your negative battery terminal.