My 1983 300SD a few months ago had a complete glow plug replacement including wires. Now, when running, the idiot light indicator flashes on and off randomly. When I first turn on the ignition, the glow plug light stays on until I hear the "click" then start the car fine...then the light starts flickering. I had thought it might be a bad connection, but then the light wouldn't necessarily stay on constantly when 1st turning on the ignition. Any ideas ?