Cadillac Repair: 85 DeVille Charging Problem, fuse block, intelligent answer

Question
First i just wanted to say what a great site, im glad i stubbled apon it.
so whats going on is my battery wont charge.I have replaced the battery, alternator, wires from alternator to battery, terminals, and it still wont charge. are there any other things i can test. i heard about a body control module having something to do with it... so if you have any ideas that would be helpfull and if you could tell me where this mystery part is that would be great too. thanks for any help.

Answer
Hi McGratts to the Max, First of all let me say this site does have something for everyone and with all the experts on board the chances of getting an intelligent answer about any topic is quite good. So lets see if I can hold up that statement and hopefully solve your chargeing system problem.

   With all the parts and things you have done it would seem that the only thing missing was the belt but it couldn't be that easy right? So lets clarify some things first. Your car is a FWD DeVille with the gas engine right? When the engine is running is the battery no charge light on? When the key is off what happens to the light? With the engine running what is the battery voltage and does it continue to drop as the engine is running? Hooking a voltmeter to the battery posts would be a good thing to do. Also if you take the cap off the B+ post on the alternator and touch your red/positive meter lead to that post with the engine running would be another good thing to try...but make sure you don't touch the alternator case at the same time or you could damage the alternator or the meter.

   A couple things you can do is check the 10A gages trans fuse in the fuse block to make sure it is ok. Then remove the wire connector from the side of the alternator and make sure the contacts are clean and making good contact. There is a possability that the replacement alt. is defective and the parts store you got it from might be able to test it if you bring it in. Otherwise call around or take it to AutoZone because they can do off-car testing.

   If none of those suggestions helps get the alternator chargeing again let me know what the light is doing so I can give you some other things to check. Bill