Glow plugs problem

Hi everyone, i got a 2003 td4 2.0 and after replacing the glow plugs, serviced the injectors ecc.. it came out that the dash glow plug is not coming on and after i checked the voltage on the glow plug socket the voltage was 0v. I tripped the relay and the current came back. I also noticed that the radiator fan came on aswell. Any idea what it could be or what i need to check. Could it be an engine management switch ?

Thanks
Kris

Coolant temperature sensor is the likely cause. Has the wire broken when you were doing the glow plugs?