I'll paste in two things here. The first is a partial posting from our very own Argve, in 2003. The second is a glowplug controller diagram, 1987 to 1994.
[FONT="]Mike... here ya go...
Since I'm pretty sure I know how your glow plug controller is mounted considering you have a banks sidewinder like I do, I will sound off the wires in the order I see them on The Enterprise. Starting from [/FONT][FONT="]11 o'clock[/FONT][FONT="] position (Passengers side Rear)
First let's get some terms out of the way...
Relay - basically a remote controlled switch. Will have 4 wires, two wires are for the coil side (control) and 2 for the load side (glow plugs/high amps)
Controller - this is the mysterious black box located under the relay, basically the brains behind the operation.
Resistor - The large zig zag looking thing sitting beside the relay / on top of the controller. This is a known ohmic value so that the controller can tell how hot the glow plugs are getting. Read my site for a little more / better explaination of this if you wish.
White wire - This is the ground wire for the coil. This wire becomes a ground when the controller wants to apply power to the glow plugs. With the key off you will have ZERO voltage on this terminal. With the key on, and WTS Lamp on, this terminal will have ZERO VOLTAGE. But with the key on and the WTS lamp OFF, this white wire will bounce between ZERO and 12 Volts. When the white wire has 12 volts the relay is not "engaged"
Yellow wires - These are the wires that supply the power for the glow plugs themselves. This are large in diameter because they must flow large amounts of current at times. If you follow these wires back in the loom, you will find that they are connected to a black connector located on the passengers side fender well / right above the tire. You will notice that on one side of the connector they are yellow and the other side the color changes to Black with an [/FONT][FONT="]Orange[/FONT][FONT="] stripe. These black wires then connect to the relay mounted on the passengers side fender wall. The yellow wires at the relay, should have power all the time, as long as the batteries are connected to the truck.
Next stop on the relay is at [/FONT][FONT="]4 o'clock[/FONT][FONT="]. You will find 2 wires here. From what I can tell they are both red but one has a Green stripe. The Red/Green wire is your key switch. So that when the key is ON, this wire will have 12 volts on it. The 2nd red wire on this terminal is the power wire for the controller.
Now continuing around the relay at [/FONT][FONT="]7 o'clock[/FONT][FONT="], we find another large lug. This lug has two things connected to it. First you see is the zig zag resistor, 2nd you see a yellow wire which leads to the controller. The yellow wire is part of the sensing system of the Glow Plug system. Remember I said it measures the temp of the glow plugs.
Following the zig zag resistor we come to another lug, on this lug you will find three wires. 2 brown wires, these lead directly to the glow plugs, and you will find a green wire. The green wire leads to the controller, this again is part of the sensing for the glow plug controller.
Now their are two other wires associated with the controller. A black wire - this is the ground for the controller and is a common place for problems so make for sure that it's grounded good. If not then all bets are off on the proper operation of the glow plug system. The other wire is a blue wire, this is the output wire for the WTS lamp[/FONT]
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