Neil wrote:the pre heater uses 3 relays and also a resistor on the pre heater plug
Hi Neil,
Thank for kicking me in the right direction, however I do not completely agree with your answer. I reversed engineered the wiring for the glow plugs today and I would like to share it with the rest of you. The wiring is quite simple. The main component is the Bosch 0333402001 glow relay in combination with a 'normal' relay. The terminals of the glow relay are as below.
15 = +12V from ignition switch
30 = +12V straight from battery
31 = Negative from battery
50 = Starter control (+12V when starter motor being enabled)
86 = Connection to glow plug relay (+12V when enabled)
K = Glow indication light on dash (negative when enabled)
G = Check wire if glow plugs are being enabled (+12V when enabled)
My relay seems to be broken. Will try to fix it by replacing the broken resistor...