Mysterious glow plug problem

[Dingo007]

Hi all...I bought a GQ 4.2na ute a while back with 330000kms. So far she's been solid with just run of the mill old ute issues. When I got it the po said the glow plugs weren't working...he replaced them himself to no avail. Haven't had to worry about until now as the cooler weather approaches...so, with some research from here, I started diagnosing....

So, the glow plug light comes on for a couple of seconds only..ever..never more than that. First start in the morning is a bitch. So I tested power to the rail...12vdc all the time whenever the key is in the on position. So I figured sticky relay....pulled the relay and it tested fine. Here's where it gets mysterious...with the key off I have power through the fusible link and to the white/red connector on the relay, nothing on the white/green like it should be. Turn the key to on and I've got power to both relay connectors and the rail!...with the relay sitting on the ground next to me! I've pulled the plug below the fuse rack and that isolates the voltage from the rail back to that plug. I even have voltage at he rail with the fusible link pulled.
Am I missing something obvious or has some bush mechanic wired another power source in? Melted wires?
Also, I assume that the "new" glow plugs will be shot?
Any help figuring this one out is greatly appreciated.

[Turtle_au]

Not sure of 4.2 but ED33(cabstar)and ZD30(elgrand)had 2 relays, 1 full voltage for initial preheat and the other through resistor for reduced voltage to maintain heating after starting.
On cabstar I changed relays to 4pole contactors, seperate cables to each glow plug and ran dual colour leds to display status of glow plug. Bright red for full voltage, dim red for reduced volts, green no volts and glow plug good, no light glow plug blown.

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