Hey phil, nice to meet you here. First i think: wow - we get international
okay - lets try to help you.
normaly the heaterlamp will glow, when there is a problem with the preglow-system (pre-heading)
- Have you allready check the glow-plugs? (in german we called it: Glühkerze, glowcandle i'll hope glowplug is the right word )
-- Check the impedance from every Plug - all the same or heavy differnces? i have no references how many Ohms Impdances they need
- Will ever Glow-Plug get power? 24V? or Less? Have only the half of zylinders Power?
-- Check where the Problem will come from. Normaly there are one or more relais. relais are aging and get damaged.