DELCO type Bridge Rectifiers

FORD type Bridge Rectifiers

HITACHI type Bridge Rectifiers

MANDO type Bridge Rectifiers

MITSUBISHI type Bridge Rectifiers

DENSO (Nippondenso) type Bridge Rectifiers

VALEO type Bridge Rectifiers

The Bridge Rectifier is the Component inside the Alternator that converts the AC current, that Alternators create, into DC power to charge the battery for the vehicles electrical system. The Bridge Rectifier uses diodes to convert AC (alternating current) into DC (direct current). Diodes are one way gates. they allow power to flow in one direction but not back in the other direction. AC current continually shifts from positive to negative, it alternates back and forth through cycles. This is why you will see electricity listed in cycles such as 50 or 60 cycles. This is the number of times per second that AC current switches from positive to negative. Bridge Rectifiers break that switching from positive to negative and allow the positive to pulse out the positive battery post and the negative pulses out through the case of the alternator itself. This is why grounding is so important in automotive electrical systems, do not overlook the ground. You can never have to large positive wire and you can never have to many grounds. The better positive and negative connections you have between the alternator and battery the less stress there is on the bridge rectifier.
Quite often you can tell when your bridge rectifier is bad. One sign is that your alternator will make a winning sound, sometimes it's a growling sound, often a bad bridge rectifier will be mistaken for bad bearings. The electrical signs of a bridge rectifier going bad is that the alternator will work much better when it's cold as opposed to hot. A worn rectifier works much better when it's cold as opposed to when it's hot.
Another tell-tale sign of a bad bridge rectifier is when your battery goes dead when the vehicle sits overnight or over several days. This could also indicate a bad battery so you need to isolate the alternator from the battery and check each separately. To test the battery you remove the battery cables and give it a good charge, then have it load tested to see how the battery holds up to the charge. You may want to do this test more than one just to make sure. The other day I did this test on my sons car, we disconnected the battery and gave it a good charge. The charge I used has a digital volt gauge on it. As soon as we shut the charger off you could see the voltage of the battery drop quite rapidly. In this situation there was no need for a load test because if the battery voltage drops that quickly when it off the charger the battery definitely is bad. This is another test if you do not have access to a load tester, charge the battery and let it set for a while without being connected to anything, if your voltage drops quite a bit the battery is bad or on it's way out. A bad battery will destroy the bridge rectifier as well. In my sons case not only was the battery bad but the rectifier in the alternator was weak as well.
The battery wire that is connected to the back of the alternator has power to it at all times, even when the vehicle is turned off. The diodes are one way gated, they let power out of the alternator but very very little go back in. As the diodes wear out that reverse leakage becomes greater and greater. It can reverse leak to the point that you will hear the alternator buzz or hum and the alternator itself can get quite warm.
The Diodes in bridge rectifiers are like car tires in that over time as you use them they wear out and do not work as well as they did when they were new.