After facing charging problems and replacing alternator and battery and cleaning all my contacts and grounds , I realized ( too late ) that the problem seems to be from the glow plug relay .It comes on , the car start fine , but i cannot hear it " click off " and the voltage indicating a low value , below 12V tells me that the plugs are still on , even after 3 or 4 minutes . Is my relay bad ? i would hate to fork out another $250 , only to find out that there was another way !
It's a 1979 300SD ( W116)