Finding a short

[Johnzi10]

Another “shake down “ drive yesterday. Ran fine till everything quit. Rolled into a parking spot. Saw the fuse link fried, so made a jumper and when started saw smoke coming from far left of the dash. After towing it so as not to further damage anything, I’m looking for advice as where to start.
I’m thinking about removing dash and cluster, then inspect. Not sure about starting and then looking for smoke source. Hope inspecting gives some clues. How would others attack this?

[Yeller]

If it made smoke you should be able to find some melted insulation. Keep following it until you find where it started

[tgreese]

The location of the smoke is your first clue. Use a bright light and get on your back so you can see under the dash. Get or buy whatever lighting you need so you can see. There are lots of LED work lights, miner's lights, etc. that you can try. You'll need to be something of a contortionist, but usually you can lie on your back and put your head down by the pedals.

Look for melted wires. Look at the location and the wiring diagram and figure out what circuit the burnt wire is in. You can remove fuses and unplug harnesses to isolate the circuits, then test the suspect circuits with your multimeter or powered test light. Inspect first, then measure using the diagram and some basic electricity knowledge.

If you melted a fusible link, the short must be downstream of that link, and before any fuses that protect the downstream circuits. Look at the wiring diagram and inspect/measure that part of the harness.

This may be easy or hard - can't say without looking at the car and measuring the circuits. You need the car in front of you to figure this out.

[Johnzi10]

Thanks Tim, I’ll tow it to the house and start the process later this week!

[letank]

Bummer, for the later FSJ, check the headlight switch, IIRC there were issues with these switches, same used in the XJ (baby cherokee)

Usually the headlights are not fused, think about driving on a mountain road at night and the headlight going blank all of a sudden. The earlier FSJs have a thermal fuse in the headlight switch, which dim your headlights so you have time to pull over, or turn them off, wait for the switch to cool off...

You can probably pull the instrument cluster off to check the mess, because of the AC vent it might be hard to take a peek!

[Johnzi10]

I have replaced the original headlight switch months ago. Have a wire around the back of the switch that sticks out the dash in a loop. I have to hold the wire to turn on the headlights because the top retaining tab is broken. I hope it is as simple as that! I just installed Holly Retrobrights, but when she broke down lights were off. I skipped putting in a relay because I thought the lower draw of the LEDs is so much lower. Two days till I can get to start the repair.

[devildog80]

Yep, the head on the pedals.....nope, kinda past that myself.

I use a retired mirror from my CJ5 to do the looking up under the dash (and a small flashlight to shine onto the mirror), or take pics now with my "phone" that I can blow up and see things closer than my old eyes can focus while near standing on my head

Hope you find the issue quick.

[Johnzi10]

I like the mirror/phone hacks! Hopefully get it towed home tonight.

[Johnzi10]

Removed the instrument cluster and found two melted wires, one red the other orange. There is a female connector that goes to the male minted on the top of the steering column. Two connectors, blue in front , black to the rear. The black one has the two melted wires. See photos!


Is the connection part of the ignition system? I have to look the circuit up in the TSM. Was hoping someone could point me in the right direction.


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[Johnzi10]

First pic shows the black connector with the melted wires. The second shows the connector on top of the column.

More pics


Better pics. The red wire is a thick gauge and is melted up thru the wire harness. Orange looks nasty and seems to head out to engine. Another pic



You can see the melted wire in the harness.
Info about the circuit and next steps appreciated!


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[Johnzi10]

I will add that the right turn signal has never worked, just recently the left turn signal stopped working. But looking at it I don’t think the turn signal has anything to do with my current problem.

[tgreese]

I think you are pointed correctly already. You need to trace the wires on the diagram along with following them in the Jeep. That's what I would do. Sorry I have no shortcuts to offer - the limited context of each of those pictures does not suggest anything to me. The plastic connectors are shown on the diagram - sometimes matching the number of wires in each connector helps to localize the circuits.

Realize that the diagram shows you the size of the wires too. There are a limited number of 10 ga red wires under the dash. Large is probably 10 ga. Look at the diagram and trace it forward from the burnt fusible link. You will likely come to a 10 ga red wire.

[Johnzi10]

Thanks Tim, gotta find correct wire diagram!

[Johnzi10]

This connector is part of the ignition switch wiring.

This is the connector in the diagram.



The orange wire goes here.



The red wire goes here.


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[Johnzi10]

I am thinking my next step is to replace the fuse link, then start to look for the short. Perhaps I should follow both wires to check that they are not grounding to anything.
I have a multi meter but am not sure how to use it ! U tube here I come.
Comments always welcome!


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[tgreese]

Maybe in the morning.

[tgreese]

These wires are all labeled with a circuit number, wire gauge and color. "12 12red" would be circuit 12, 12 ga red wire. There is a table that tells you what the circuit numbers correspond to. If the color says "TR" that's with trace, IOW a stripe.

Tell me if I've got it.

The 18 ga green fusible link from the starter solenoid to splice B2 has fused. Splice B2 goes to the ignition switch via a 12 ga red wire. The 14 ga orange wire connected to the run side of the switch goes to the heater motor fuse. The heater motor circuit is a dead end here since it is protected by a fuse, and that would have protected the fusible link.

The #12 14 ga orange circuit branching before the heater fuse has to be the culprit. That connects to splice B6 which is shown on the Emissions page of the diagram. There are three devices fed by splice B6: the choke heater, the carb bowl vent, and two solenoids, one for the vapor recovery vent and one for the fast idle (anti-diesel?) solenoid. Your short is probably between B6 and these devices, since they all go directly to ground and would not have burnt up the wires.

I have heard of the electric choke wire shorting out before. That would do it. Note that the wires go from the ignition switch and through the firewall bulkhead connector and under the hood. Not sure what the bulkhead connector is like, but it's probably like the earlier models. I presume that symbols D4 and B6 with the heavy black box are bulkhead connections going through the firewall. If the wires under the hood to the emissions devices are not burnt, I would expect the short to be under the dash, before the wires go through the bulkhead connector.

Note that the short could have been intermittent, and moving the wires around could have fixed it. Best if you can find the short location by inspection. Any wire downstream of the short will be undamaged - you've got that principle?

Just me - I would first find the short and isolatre the burnt wires before doing anything at the fusible link. You can jumper the fusible link with a clip lead to test it; these are cheap and handy. https://www.amazon.com/WGGE-WG-026-Piec ... 110&sr=8-3 They used to sell them at Radieux Shaque, but that's gone ... maybe a local electronics store, or from Amazon.

[Johnzi10]

So I’m thinking that I should remove the steering wheel (have to replace turn signal switch anyway) and inspect the wires I the column. Still need to isolate burnt wires, follow and inspect, but I want to see past the connector.

[letank]

if the late models are similar to early 80's, the ignition switch is toward the base of the steering column, roughly to the right, above the brake pedal, not inside the steering column where the key is inserted.

If you have room try to separate the melted wires with a razor blade to identify the various damaged sections

a quick way would be to disconnect that orange wire from the starter solenoid and test with the DVM the wires for a short between the starter solenoid feed to your under dash melted section.

[Johnzi10]

Got back to the Wagoneer. I have melted wires ( too bummed to look at which circuits they are. Any tips on dash removal for access to the harness up to the firewall is appreciated. I seem to remember that to truly remove the dash, the window needs to come out. I need access to repair (hope not replace) the melted mess. Someone got a lead on harness?