Hello. The dash battery light is on and flickers while driving. NO trouble starting and runs FINE. Auto parts store says alternator is bad. I want to find the specific problem... regulator, brushes... What is the best way to test the regulator (mounted to back of alternator) to see if its bad? And how do I access the brushes? Would new brushes designed for Ambulance system be compatible? I'm having trouble finding basic brushes. Any help is much appreciated.

It's likely the brushes are worn down too far. However, the voltage regulator/brush assembly comes as a unit. Since it's an externally mounted assembly, it should be easy to remove and replace on the vehicle. Simply disconnect the negative battery cable and use a Torx T-20 driver to remove 4 mounting screws. Use a small drill bit to hold the retracted brushes in position during installation. Once installed, simply withdrawal the bit. Remove any ridges on the shaft (rings) with abrasive cloth.

Try salvage, if you cannot find a new voltage regulator/brush assembly at your local auto parts store.

The best way to test the regulator is to check the regulated battery voltage, which should be 14 to 15 volts.