OPSU is in, but no wire.

[Subourbon]

Hey guys,
Got a K20 suburban back in January, too cold to do anything with it until recently.
Mechanically, I get by, but electrical I am useless.
There are a number of issues,
Fuse for horn sparks immediately as I put it in, i got a short somewhere, doubt I'll ever find it, relays somewhere I am guessing, I cleaned my ground in engine compartment yesterday. I think they're all ok.
Only gauge that works is speedo, I took apart the cluster, cleaned it, the PCB has a few rough spots, tips on how to fix it would help a lot!
I see wiring diagrams here there but this truck was used as a volunteer firefighter truck in Yukon, then absolutely ignored by a hunting guide somewhere in Canada, so a lot of the wires have been chopped, spliced and I've counted as many as 3 wire color changes, just in the engine compartment. So i really dont know what does what, any tips on efficient tracing?

And finally, I'm.fairly certain I located my OPSU, around filter housing, has an end for a clip that looks similar to my glow plugs. Problem is, I see no wire, nothing loose or dangling or anything. Which wire coming out of the rats nest of is supposed to go to the opsu, i changed the oil, synthetic, so I'm not too worried, but still I like things that work!

And very embarrassingly, I see no have high beams. How do I turn them on? It's a suburban diesel Scottsdale 1982. I have zero literature and white knuckling taking my dash apart and tracing each wire.

Thanks everyone, stay safe,

 

[Turbo4whl]

And very embarrassingly, I see no have high beams. How do I turn them on? It's a suburban diesel Scottsdale 1982. I have zero literature and white knuckling taking my dash apart and tracing each wire.

Thanks everyone, stay safe,

High beam switch is on the floor, foot switch, upper left.

 

[Subourbon]

Now I know what that's for, thank you very much!

 

[Turbo4whl]

With the cut up wires, well you are going to just roll up your sleeves and dig in. Speedo is mechanical, no wires needed.

 

[Subourbon]

Thanks turbo4whl.
Made some decent progress yesterday. As far my opsu, can I just buy a wire ending that clips onto the sensor and run through to the instrument panel clip number, for example if oil pressure gauge is #9 then find where that wire goes, add the clip I need and connect it to the unit?

 

[Turbo4whl]

Yes, find the correct wire, add the clip and your good. If you cannot locate the correct clip, you can make the connector. Use a female spade lug connector. Spread the connector until it fits over the button connector on the sensor.

 

[AuroraGirl]

What is an OPSU

 

[Turbo4whl]

@AuroraGirl

The OP (original poster) should realize that abbreviating the most important part of their statement, may be confusing to many readers.

OPSU = oil pressure sending unit

 

[bucket]

@AuroraGirl

The OP (original poster) should realize that abbreviating the most important part of their statement, may be confusing to many readers.

OPSU = oil pressure sending unit

I'm glad you know what's going on. I couldn't figure it out, lol.

 

[AuroraGirl]

Team Clarity!

 

[chengny]

I show

Hey guys,

And finally, I'm.fairly certain I located my OPSU, around filter housing, has an end for a clip that looks similar to my glow plugs. Problem is, I see no wire, nothing loose or dangling or anything. Which wire coming out of the rats nest of is supposed to go to the opsu, i changed the oil, synthetic, so I'm not too worried, but still I like things that work!


Thanks everyone, stay safe,

I show the lead to the oil pressure sender as a TAN 20 AWG. See .5 TAN 31 below:

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It transits the firewall connector at the bottom row, inner bay of the engine harness block. Like this:

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[chengny]

Fuse for horn sparks immediately as I put it in, i got a short somewhere, doubt I'll ever find it, relays somewhere I am guessing, I cleaned my ground in engine compartment yesterday. I think they're all ok.

Thanks everyone, stay safe,

On this one; don't be so quick to blame the horn control circuitry. There is another branch circuit on that fuse - the cigarette lighter. And it is notorious for getting shorted to ground. Try unplugging the single orange lead from the base of the lighter and see what happens.

The dome light and clock (if equipped) are also supplied by that fuse.

 

[chengny]

Only gauge that works is speedo, I took apart the cluster, cleaned it, the PCB has a few rough spots, tips on how to fix it would help a lot!
I see wiring diagrams here there but this truck was used as a volunteer firefighter truck in Yukon, then absolutely ignored by a hunting guide somewhere in Canada, so a lot of the wires have been chopped, spliced and I've counted as many as 3 wire color changes, just in the engine compartment. So i really dont know what does what, any tips on efficient tracing?


Thanks everyone, stay safe,

First check the fuse labeled GAU/IDLE. Its located up near the top on the LH side of the fuse block:

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Next check that the instrument cluster is grounded. The common grounding bus block is on the LH cab sidewall - above the parking brake operatorhhhhhhhhhhh:

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BTW - the speedometer is purely a mechanical device so it won't be of any help in diagnosing the lack of gauge function. Does your voltmeter work? The voltmeter doesn't use a sensing leg like all the other gauges. It only requires a hot and a ground. Like all the other gauges, the hot is from the GAU/IDLE fuse and the ground is to the bus block. So if the voltmeter is working that confirms power and ground to the IP. The other gauges must have sensing problems.

See what happens when you wire up your new OPS.

 

[Subourbon]

That is amazing, yes indeed, I found a ground, I'm still a ways from sticking the panel back in there now.
And yes, my apologies opsu, oil pressure sending unit. I did so many Google searches on the thing a d saw it labeled as that I guess I picked that up. Apologies everyone.

Well, gauge, no news yet, still in the basement, I did find a few rough spot, I tried a window defog repair kit, we will see.
And the horn, well like insaid previous owner chopped it up to a point where nothing is the original wire colour, although the pics of the fuse box are a massive help coz I cant read a damn thing on mine.
But I removed horn relay, cleaned up the horn ground just forward of the radiator shroud cover, put a new fuse in and... nothing. No spark, nothing. Mind you, nothing at all works on it because the batteries are drained, the truck is entirely silent, no buzzer no fuel pump no glow plug when I turn the key. So now, horns and gauges just went down on my priority list.

 

[Subourbon]

Sometimes it's the simplest things.... this battery killswitch, or breaker to switch batteries on and off was flipped over to off, I guess I knocked it when checking passenger side horn.
I dont know if all models have them or what but.... flipped back to on, glow plugs, lights buzzing, and she fired right up.
In other news, the horn works. I cleaned up the grounds just forward of the radiator shroud that bolts the horn in place.
Also removed the relay in the cab, brushed off some dirt and crud.
I guess it wouldve worked yesterday had I not switched the entire thing off. I dont know which fix did it, if it was cleaning up the relay or the ground, but it works!

Heres a pic a of the battery switch, just above the passenger side horn and a tiny bit further back. Now onto new things, oil pressure.
thank you to those who posted explaining things, electrical really sucks,

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and stay safe, if this thread is still open I'll let you know how it goes.