Hi,
Had the same problem with a 200tdi fitted in my series 2a landy.
Glow plug warming light wouldn't come on with the red/white wire connected to the starter solenoid.
But if I disconnected the red/white wire the Glow plug warming light would come on and the relay would switch off the Glow plugs at the right time.
I figured that the red/ white wire should be connected to the other side of the starter solenoid. The side where the power goes to the starter motor.
My reason for this is before when the red/white wire was connected to the starter solenoid on the Spade fitting, this was getting power as well as the relay.so it was telling the Glow plugs and relay to turn off. Hence why the Glow plug light wouldn't light up.
When fitted to the other side the red/white wire will get power when you decide to start the engine and therefore tell the relay and Glow plugs to turn off.
This would make sense as you might want to start the engine without the warm up cycle, because the engine Is already warm or its hot outside.
Hope that makes sense
