Volvo Repair: 1989 volvo 240DL charging system, volvo 240dl, load test

Question
While driving the car looses power then shuts off. We have replaced the battery and alternator with no results. With the new alternator in place it was charging at about 12.5 volts. Is it possible that the black wire from the oil switch could cause this? Also where should that be connected?

Answer
  No, oil switch  will NOT shut down vehicle. (This is not your father's Oldsmobile) 12.5 volts is too low. Should be 13.5 or higher while charging. Up to 15.8 volts while charging. Load test the battery and then check your cables/connections. Especially the grounds.

Mark