This is the glow plug relay. Power to the glow plugs goes from copper terminal with the big red wire on the right to the copper terminal on the left which feeds the glow plugs and wait to start light.
If the relay is good but the controller is bad, you can jump positive battery voltage to the terminal with the bright pink wire and the relay should click, the wait light light go on and if the relay contacts are not burned, the glow plugs will be energized as long as 12V is put on the bright pink wire terminal. The relay contacts may be burned so that little power is sent to the glow plugs but the wait light may light. If the relay contacts are burned, you can jump across the two big copper terminals with a heavy wire (red wire size) and battery power will go direct to glow plugs and wait light.
Depending on temperature jump 7-10 seconds, no more.
Note that the bright pink wire below is a power source from a momentary push button under the steering wheel to manually power the glow plugs on my truck. The dirty pink wire with rubber connector is from the controller and is disconnected to protect the glow plugs from the controller running away and not disconnecting after 7-10 seconds.
You must be registered for see images attach
