dashboard glow plug light

[Dodg]

the light has stopped coming on. when i try to start car , engine just mumbles at me then stops 

could this be the plug module , i tested the brown an black wires an got 12v 

but its not on the dash display

any help will be much apreciated

[Carl Gibbs]

Strange, I always thought that the light would come on when the glow plugs were warming up. 

If the car is not starting, then maybe the glow plugs are all out and not warming up, hence no light, however, this seems strange that all of them would go together.

What mileage is on the car and is there any service history of glow plugs replacement?