glow plug or relay diagnostics?

[wabashofutah]

The F350 is still a little dog to cold start unless i've left it hooked up to the block heater all night. I'm assuming the glow plugs are bad but I realize it could also be a bad relay or controller. Are the relay and controller 2 different components? How can I test the glow plugs and the relay/controller? Voltage numbers/detailed procedures would make my day

 

[trucknorris]

relay and controller are one unit; well two separate things bolted to each other and sold as 1 unit. the way to test it is to test each glow plug individually for spec resistance. if in spec, test power to the glow plugs when you turn on the key on a cold start....
if your gp controller is bad, your in-dash voltage meter will read "normal" (not read close to 0) when you turn the key on, as you wait for wait to start..
on a working gp controller, and working glow plugs, your in dash voltage will hoover at around 0 for couple of seconds, before you hear a click..

 

[Agnem]

This has been outlined many times. Do a search.

 

[gatorman21218]

a good plug will read less than 1 to 2 ohms