Alternators make AC (alternating current), just like the electrical outlets in your home. Then, it uses a bridge rectifier (rectifier) with diodes to convert the AC current to DC current for use by your vehicles electrical system, mainly the battery. This AC to DC conversion process is a real point of stress for your alternator. The greater the power demand from the electrical devices connected to your vehicle the harder it is on the bridge rectifier (rectifier). Fact is, the rectifier is the number one component that fails on high output alternators. By connecting two rectifiers in parallel we have doubled the load carrying capacity of the alternators bridge rectifier.