QuestionI have an 1986 Chevy 1008. The other day the battery grounded out and caused a power failure. Now the glow plugsrwon't heat up. I have power to the top of the relay, but not at the bottom. I know the relay is good though as it worked on an other vehicle. What are the two small wires going to the relay?Could they be my problem? Or could I just be getting 12 volts to the relay? ( I didn't check that) Thanks!!!
AnswerHello Rusty,
12 volts is what you need at the relay. Some 1008's have a large resistor across the firewall that the glowplug wire goes through, which is connected to the second, or 24 volt side of the battery system. A volt meter connected there will show 24 volts, but when the relay closes, and the glowplugs put a load on the wire, it drops down to 12 volts.
The other 1008's get their power from the middle of the batteries, which is 12 volts.
The small wires are what operate the relay, and one small wire goes to the wait light.
The controller for the glow plug relay is up above the brake pedal. There is a plastic box hanging on the wires. It is about one inch thick, three inches wide, and about five inches long. The cap comes off the end, and there is a circuit board inside. Pull that board out and look near one end at a diode that is soldered to it. They burn out occasionally. But generally speaking, they are pretty dependable. Check for a blown fuse in the fuse block near that controller.
I will also say here, for your future information. Just about 100 % of that truck is stock Chevy 12 volt stuff. Even the alternators are 12 volt, 100 amp alternators, and are completely interchangable. The only difference is the right side alternator is NOT grounded to the engine, but is rather grounded, (or more correctly, connected) to 12 volts. The left alternator is grounded to the block.
What happens is, the left alternator charges the front battery, and the right alternator charges the rear battery.
If you ever need to jump start the truck, just connect jumper cables from a standard 12 volt truck, to the front battery posts.
The only true 24 volt item is the starter and solenoid. Even the starter relay under the dash is 12 volts, but controls 24 volts to the starter.
Now, I don't know what grounded out on you, but there are some fusible links, mostly near that diamond shaped power tap on the firewall. They carry the power to various things, and the one supplying the glow plug circuit and fuse block may be blown.
Good luck, and write back.
Van fixitfox33@sbcglobal.net
