TonkaJKU Posted April 18, 2020 Share Posted April 18, 2020 Im working on my sons 88 YJ. When you turn the key the dash lights come on and everthing looks good. When you turn the key you hear a click and everything goes black. You have to disconnect and then reconnect the battery to get anything back on in the dask. We have replaced the starter, ignition switch, locking cylynder, all 3 relays. The back of the fuse box and the bulk head connectors look like they are melted, the metal pins are mostly gone. So my questions are... What caused this and how do I fix it? Any help would be great. Thanks Quote Link to comment Share on other sites More sharing options...
TonkaJKU Posted April 18, 2020 Author Share Posted April 18, 2020 Preview attachment 20200418_144137.jpgPreview attachment 20200418_144611.jpg 20200418_144611.jpg 4.8 MB Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted April 19, 2020 Administrators Share Posted April 19, 2020 Hi, TonkaJKU...You're describing a major short that likely started between the key switch and power distribution box (fuse/relay box). The cause of such a short can be bad insulation on a heavier lead. A lead likely got very hot and melted the insulation, enabling a short to ground that arc'd and melted insulation at the adjacent wires in the circuit. Rarely but possible, the bulkhead plug itself develops a voltage leak between pins and shorts wires; the shorted wires melt into the harnesses. Before doing any further testing, all battery power must be eliminated. Disconnect the negative battery cable then the positive cable. Keep the battery off-line while performing any electrical tests. The best test equipment for a short of this type is the use of a non-destructive insulation resistance test. This sounds complicated but really isn't. The issue buying the meter, which can be very expensive. I have worked with a Fluke 1587, which you may find used. This is a professional grade volt-ohmmeter that electricians and generator system techs use for testing a short to ground or bad motor/generator winding within a closed system: electrical conduit, inaccessible cable routing, within an assembled electric motor or generator, or inside a steering column in your case. All battery power must be eliminated before conducting this test; disconnect the negative battery cable then the positive cable. A Fluke 1587 or similar Fluke meter is self-powered by a 9-volt battery. The meter can send high voltage current in the 50V to 1000V range through a wire or wiring circuit. Again, this is "non-destructive" current because the amperage is ridiculously low with the only power source being the meter's 9 volt battery. A shut off 12VDC circuit can easily be tested at 50V, higher if a tiny leak is suspected between two parallel wires. Using this test, no damage to the wiring will occur while you are trying to find a wire or circuit that has a short to ground. Since your wire(s) are apparently shorted already, you can likely forego the expense of a 1587 and use a simpler volt-ohmmeter to check individual bulkhead pins for shorts to ground. Here you simply want to see if a pin is completing a short to ground. With the vehicle's battery disconnected, you are checking continuity between a pin and a good ground. If the pin normally carries current (positive) and now reads a complete circuit (through the meter) to ground, that wire is shorted to ground within the system. I could not link to the photos, but you can post them in this topic by using the "Attach" provision at the bottom of your post or reply. Given what you describe, it's obvious that the short involved high enough battery amperage to burn the entire bulkhead plug. Before doing anything else, with the battery disconnected, you need to know where and how much wiring melted. It could be the steering column to bulkhead wiring, the bulkhead plugs (both sides of the firewall) and/or wiring from the bulkhead toward the power distribution box. If the harness damage originated at the key switch and traveled down the column, the short may have begun with a defective key switch that shorted to ground or a loose switch that shorted hot wires. Unwrap the tape and convolution tubing at each side of the bulkhead plug to see how far the wiring is damaged in each direction. Strip back tape/tubing just far enough to get past the melted section(s). Unless the damage is limited to the bulkhead plug, you'll likely be looking for a donor harness from the ignition switch to the bulkhead plug and possibly spur wiring that goes from that harness into the wiring behind the dash. You can tell how far wiring needs replacing by tracing the melted wires. An FSM wiring harness schematic will help trace which wires to inspect for insulation burn-through. When the short took place, it was a wire circuit carrying enough amperage to burn or melt either a single wire, a single wire and several adjacent wires, or the bulkhead connector. If you would like to attach photos to your topic, please do so. I would be glad to comment... Moses Quote Link to comment Share on other sites More sharing options...
TonkaJKU Posted April 19, 2020 Author Share Posted April 19, 2020 It wont let me upload the photos. I hit inser image from URL and them paste my web address and hit insert and it thinks for a sec then turns red Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted April 21, 2020 Administrators Share Posted April 21, 2020 TonkaJKU...I checked your Member adjustments...You should be able to upload photos now. I will watch for the post... Moses Quote Link to comment Share on other sites More sharing options...
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