94 Transport Alt not charging battery

My 94 transport is having electrical issues again. The alt has been tested and is fine the battery is brand new ( so is the alt) The alt is not charging the battery. Last time this happened it was a wire that i had snatched loose under the motor. I dont have a mechanic here now that knows how to trace this out. Im sure my husband and I can do this if i know where to look and what might cause this problem. HELP PLEASE i need my van kids in a blazer doesnt work