The regulator limits voltage as to not damage the battery and the electrical components. The rectifier converts AC voltage to DC voltage, which is used to keep the battery charged and to operate the electrical system. Symptoms of a failed or failing regulator/rectifier include the battery not properly charging, hard starting, and blown out light bulbs. Among the over 250 million registered vehicles on American streets, roads, and highways, more than half of them are used for work and commercial use. For those who rely on their vehicles for business, Discount Starter & Alternator is here to keep you on the road and off the tow hook. We sell brand new replacement rectifier/regulator units for commercial trucks, vans, buses, tractor trailers, and other heavy duty work vehicles from major manufacturers including Chevrolet, Freightliner, GMC, Isuzu, and more. Browse our extensive online inventory and shop with confidence at Discount Starter & Alternator.