How Do You Check Alternator By Disconnecting Battery. So how to test alternator by disconnecting battery. First park the car in a public yet safe place.
And then unplugging the positive connection of the battery. The instant you disconnect the battery cables to test the alternator the alternator goes into full field mode where it can generate a voltage spike as high as 150 volts. In the pre-computer days you could pull it off without damaging anything.
Using 10-gauge wire to which solderless ring terminals have been installed connect the output bolt on the back of the alternator to the positive terminal of the battery.
If it dies you have a weak alternator if it stays running your Alternator is working as it should. Be careful doing this though because there are a lot of moving parts in your engine compartment that could cause injury. A battery test is easy to perform and can be done at home. How to check if alternator is draining battery.
