having problem with volt drop

[2000grandprixgtp1924]

hey guys I have a 2000 gp I was having problem when I was driving my car the voltage would drop to nothing I would lose power to my dic my areoforce and my radio and windows and sunroof. and then after amin or so then it would come back on. so I got to thinking that it was the alt. so I pulled it off and had it checked and one of the 4 time it failed the test so I put a new one on it. then was still having the same problem so I got to thinking about it and cleaned the batt coneters and they where both dirty so I cleaned them and I am still having the same problem. please if anyone can help with this I would be thankful

[2000grandprixgtp1924]

its like the hole car loses power when it happens

[Explicit_Spade]

Sounds like a bad bcm to me.

[cooper]

Electrical problems can be hard to diagnose without actually being there.. If you have a good DMM you can pretty much narrow them down. Start off at the source The battery cause batteries sometimes have a weak or even dead cell. Check the voltage of the car without it running in the middle of the battery terminals after you clean them... Then start working out to the end of the connectors you should not even see a voltage drop.. corrosion loose terminals wires etc are the leading cause of most electrical problems and are normally reasons for part failures.. Start the car up turn on the lights to check the alternator 13.8 to 14.2 is approx. what you should see. A good battery will read above 12 volts like 12.5 to 12.8 with a full charge...The good part here is most auto parts places will check parts free but my experience is usually been with loose or corroded wires that give you electrical problems. Below 10 volts and that engine will start doing all kind of weird things ,misfire,shut down etc.