I have a '93 Nissan Sentra. A few weeks back I began smelling a sulphur or "rotten egg" smell. Eventually my car died. I had the battery replaced but they told me my altenator was also testing bad. Carried to AutoZone who tested and said altenator was over charging. Bought altenator and had friend put it on. After a few days, the car began to make "sounds." Brake light began to burn all the time on dashboard, followed by battery light. Then the radio, heater, speedometer, etc. quit. Had friend look at it who found two loose wires to battery. Checked everything again - all was running well. Until I tried to drive it home last night and then EVERYTHING began to quit on it again.

What could the problem be?