83 GMC Stepside

[juggernaut6625]

Hey guys I just bought an 83 step-side. Im going to slowly go through all the kinks until I have a completely solid daily driver. I dont intend to make it a show truck at this time. One of my main issue being in louisiana is my windshield wipers dont work. i had the oscillation board rebuilt and bought a new switch and it worked for about 3 minutes. The other dash issue is my gauges. The speedo bounces and then when off it settles an inch or so below the 5 mph mark. the fuel gauge only goes up to a third full. oil pressure is pegged out and temp is  all the way cold lol. Im replacing the entire electrical harness this weekend since one of my main wires caught fire the other day, I replaced it and the new wire caught fire again lol. I wanted to replace it anyway so i just bought the 400 dollar kit and will replace the whole thing. I know this is alot of erratic info but any tips would be helpful. once i get this electrical thing done i will tackle this stuff in more focused attempts.

[bd]

...Im replacing the entire electrical harness this weekend since one of my main wires caught fire the other day, I replaced it and the new wire caught fire again lol. I wanted to replace it anyway so i just bought the 400 dollar kit and will replace the whole thing....

Begin with this ^^^^.  Figure out what caused the wire to melt or you might destroy the new harness and burn your truck to the ground!

...my windshield wipers dont work. i had the oscillation board rebuilt and bought a new switch and it worked for about 3 minutes....

Check the w/wiper switch ground connection to the left kick panel, behind the dash.  The instrument cluster and gauges share that ground connection, so disassemble and thoroughly clean it.

...The speedo bounces and then when off it settles an inch or so below the 5 mph mark....

Common causes of "bouncy" speedometer needles

...the fuel gauge only goes up to a third full....

How "full" is the tank?  Unplug the signal wire from the fuel tank sender.  With the ignition switched on, the gauge should sweep past Full to ~3:00 o'clock.  Ground the signal wire to the gauge.  The gauge should sweep to Empty.  Does it?  If the needle remains stationary, check the gauges fuse.

...oil pressure is pegged out....

The signal wire from the oil pressure sender is open - possibly unplugged, a faulty sender, bad connections through the instrument cluster connector, or the signal wire is severed.

...temp [gauge] is all the way cold...

The signal wire from the coolant temperature sender is open - similar possible causes as those listed for the oil gauge, or the wrong type of sender is installed.

[juggernaut6625]

I appreciate you breaking down all my issues and responding to all of them. My initial concern with replacing the harness was that i would just burn up a brand new harness. Then I was told that the only wires that could cause that kind of back feed were contained in the harness, so by replacing the entire harness I should be able to eliminate having to trace each wire individually. The wire that caught fire went directly from the positive battery terminal to the "power block" (i believe this is what it was called) in the center of the fire wall.

[juggernaut6625]

Also the tank is full when it read 1/3rd full. could the sender just be dirty and not floating any higher?

[bd]

I appreciate you breaking down all my issues and responding to all of them. My initial concern with replacing the harness was that i would just burn up a brand new harness. Then I was told that the only wires that could cause that kind of back feed were contained in the harness, so by replacing the entire harness I should be able to eliminate having to trace each wire individually. The wire that caught fire went directly from the positive battery terminal to the "power block" (i believe this is what it was called) in the center of the fire wall.

That's really bad advice! 

Your description implies that the wire that burned is a fusible link.  The fusible link is a high surge capacity, slow-blow fuse.  It's purpose is primary circuit protection of the medium-current B+ buses to prevent the vehicle from burning to the ground due to an electrical fire.  Often, but not always, there is secondary circuit protection for individual appliances in the form of lower rated serviceable fuses that are redundant to a fusible link.  But for some circuits, secondary protection is not installed and the circuit components must rely on the primary fusible link for circuit protection.

Familiarize yourself with the 1983 Wiring Manual to help determine what's causing the electrical fault.  It maybe related to poor wire routing or a shorted appliance.  Perhaps a PO installed "custom" wiring that's at fault, but not part of your new harness.  A wire could be pinched between the engine and transmission bell housing, or burned against the exhaust.  Perhaps the alternator is shorted.  You get the idea?  You need to figure this out before installing a new harness for a repeat performance.  It shouldn't be too difficult to sort out.  Besides, becoming familiar with the factory wiring diagrams will help you install the new harness correctly.

Regarding the fuel gauge, perform the simple grass roots test I suggested and report back.  The test should indicate whether the fault is up toward the gauge or down toward the sender to help you focus your efforts.

Edit: clarity

[juggernaut6625]

Ok, Ill ensure to go wire by wire to check for pinched burned or shorted wires. I'm unsure on how to check accessories or components for shorts. Especially since half of my truck has no power because my fuse box was fried. I have looked over the diagram several times when fixing my headlights but please humor me when I ask this lol. The proper diagram for me to be looking at is the ck truck 1 and 1A, then 1C through G which are the component and switch diagrams correct? Once again thank you for taking time to respond to these issues BD.

Also my A/C blower just recently was acting funny, cutting on and off. Is that possibly the short? Would it have enough juice to light that wire up like a Christmas tree?

[bd]

Ok, Ill be sure to go wire by wire to check for pinched burned or shorted wires.  ...half of my truck has no power because my fuse box was fried.

The proper diagram for me to be looking at is the ck truck 1 and 1A, then 1C through G which are the component and switch diagrams correct?

Also my A/C blower just recently was acting funny, cutting on and off. Is that possibly the short? Would it have enough juice to light that wire up like a Christmas tree?

You shouldn't have to inspect wire-by-wire.  Use the wiring manual to help guide your search.  The entire fuse box is "fried" or just a few connecting wires?  Use the observed damage in conjunction with the wiring manual to help you focus your attention on the offending circuits.

Yes, to your question on the relevant pages in the wiring manual, but you need to be selective.  Not every diagram in that section will apply to your truck.

A short circuit can place incredible strain on the wiring, sometimes in unpredictable ways.  But on a 34 year old truck, you should be prepared for more than a couple of appliances simply to be worn out.

[juggernaut6625]

Understood, Im just curious as to which appliances it could be. There arent very many electrical components on the vehicle. Do i need to check all the stuff behind the dash? I guess what im asking is what are the limits to having a back feed strong enough to catch a wire on fire in literal seconds. That's a lot of juice lol. My thoughts would be anything on the other side of the fuse box would most likely not have enough capacity to do that. And the left side(from inside the cab) of the fuse box gets no power. So no ignition, turn signals, hazards, or seat belt light/buzzer. Also all fuses were checked to make sure nothing was blown.

[bd]

So, your fuse box isn't fried, it just has some dead circuits.  That fuse link feeds the ignition switch and fuse box.  Pick up a 20-amp auto-reset circuit breaker (image), 3' of 14-gauge wire, some ring terminals and a couple of alligator clips.  Cut the wire in half.  Install one ring terminal on each wire and connect the wires to the studs of the breaker.  Connect the alligator clips to the free ends of the wires.  Unplug the ignition switch.  Cut out the melted fusible link and substitute the circuit breaker in its place.  See if the breaker continues to pop.  If it doesn't, plug the connectors into the ignition switch one at a time and see what happens.  You are trying to isolate which part of the circuit causes the problem.

Edit:  added image

[juggernaut6625]

I'm finally getting into this. School and life have been hectic. I have the photos of damage that i planned to post but even zipped individually they are too large. I plan to disconnect the whole A/C wiring because of the damage. If nothing trips the circuit then i will tackle the A/C system.

[roundhouse]

It's not back feed that's melting wires

It's a direct short to ground

[juggernaut6625]

I believe I found the culprit. The fusible link to my starter was contacting my header and is burnt to a crisp.

[roundhouse]

I was gonna suggest checking the starter
There's lots of wires connected there

I much prefer the ford version where the relay is up by the battery and the wires to the starter are not energized all the time