charge system is good yet fails to work

[74302bronco]

just to start out i have already search and found nothing to help me out exactly. my 74 bronco isnt charging the battering. it started about a month ago when i left my lights on for 3 hours. i quicked jumped it and drove down the road and it died on me. took it to shucks they said i need a new battery. got a new 770cca battery and was fine for about 2 weeks and then one day after work it wouldnt start. jumped it got home turned off the engine and it wouldnt start again. so i jumped it and took it to schucks and they said i need a new alternator, so i got a new alternator. before i took the old one out i took some readings. at idle it was at 11.8 volts. with the new alt installed it went up to 12.2 at engine off and on, when i reved it it would spike 14 volts and quickly drop right away. with my heater and lights and stereo on it would drop to 11.8. all wires seem to be good although there are a couple wires just hanging around that arent in the charging system but i dont know where they go. oh and i took my old alternator to get tested and it tested good at 14.96 volts. everything is only about 4 years old after a frameoff. sometimes when i turn the key just to the on position my stereo doesnt come on and i have to push a button to get it on. but other times it comes on automatically.
my 02 ranger at idle is 14.00 volts easy. also on the alternator the only connections i need are the battery, field, and grnd. right? i think there is an extra TA and one unlabled that is not being used. i have an external regulator. what do i need to look at. should i keep my new alt for the slight improve or use my old one. let me know if you need to know anything else. before i left my lights on for 3 hours i ran and started like a champ. thanks agian

[blwngsket]

I had a similar problem with mine. Couldn,t figure it out to save my life. After about the 3rd or 4th time of checking and re-checking I decided to disconnect the the wire harness plug that is apprx 4 to 6 inches from the alt. and it fell apart in my hands. Totally corroded. Couldn't tell by looking at it. I removed the plug and soldered the wires together and the problem was gone. Hope it helps. Good Luck.

[74302bronco]

what does your battery read when engine is off and on.

[Scodge]

Step 1) Check your grounds

Step 2) Install a good voltmeter full time. This way, you can see what is happening with your charging system as you drive. Otherwise, there is no way to moniter your charging system in real time.

Step 3) Upgrade to an internally regulated model. A 12si Delco or a ford 3G are the most common. Newer electronically regulated models charge way better than the old alternators with seperate mechanical voltage regulators.

If you know for a fact that your alternator and battery are working properly, then you have some sort of voltage drain. You need to do one of the checks for voltage leaks. First step is first, though. recharge your battery, check your grounds, and run the truck for a while with a voltmeter installed. Then you'll be able to see when your system is and isn't charging.

[mantoani]

as scott said check the grounds. check the connection between the block and the neg cable, it is often overlooked. might help.

Craig