Have tried finding a thread on this but no luck. Just started the car and when I turned the key no glow plug light. So waited 10 seconds tried again no warning light. So I tried starting it and the engine started fine, (outside temperature 19 degrees C). Then after about 20 seconds of running, the light came on for about 10 seconds then went out and remained out. When we returned to the car later the same scenario happened again. Does anyone have any ideas?