OK, Had some time to play with it today, Seem's the controller is bad cause i have 12 volt on the white wire and 12 volt on the others but when i cannot get 12 volt on the busbar side going to the glowplugs when the key is on the run position. So i am assume the controller is bad. This is on a 1992 7.3, what part # controller and where to get it from, also what kind of price to expect?
Try the following.
1) Turn the key to on, you should have +12v on the small post with the red wire on the GP controller.
2) Use a jumper wire from the negative post on your battery to the the small post with the white wire. The solenoid should now click. If it clicks it is now connecting the two large posts together. If it does not click replace it.
3) Some reasons your controller might not be working -
a) You have 3 or more glow plugs that are bad. (So the controller is not turning on the glow plugs.)
b) One or both of your glow plug wiring harnesses is bad. (So the GP controller is not turning on The glow plugs.)
c) Your controller ground wire black or brown wire (Can’t tell from the pic.) is not making a good ground. Thus no ground can be made via the white wire to activate the relay.
d) The controller or the relay on top of it, is not working and needs to be replaced.
I hope that helps.