http://dieselplace.com/forum/  might be able to help.

Greetings,

You can find the relay for the glow plugs in the master fuse box under the
hood.  The chart for the fuses and relays is inside the cover for the box.
You should also be aware that there is a glow plug controller that can go
bad and cause problems with your glow plugs short cyling or not cycling at
all even if you have good power.  In addition, there could be a problem with
the ignition switch, the ECM or even the coolant temperature sensor
preventing the controller from cycling the plugs.

Cheers - Jonathan