I bought a 98 Jimmy last weekend, to be my son's first vehicle. The drivers door pins were so bad that it broke the door jamb switch for the interior lights. I replaced the door pins, and replaced the door jamb switch. No lights, the fuse was blown. When I put a new fuse in (courtesy lights) the vehicle powered on... without the key in the ignition. It acted just like I had turned the key to the "on" position. If I crank the truck with the fuse installed, it will not turn off when the key is turned off and removed. As soon as I pull the fuse, it shuts off. Could this be tied to the electrical ignition switch? Any advice on where to start?

 

How was the truck running before you fixed the door?

When you put that fuse in what turns on?

George

 

The truck runs and drives perfectly fine when that fuse is not installed. With the key removed from the truck... when I install the (courtesy lamp) fuse, it acts exactly like I've put the key in and turned it to "on". All electrical systems power up, including the fuel pump priming.

 

Ignore this post

 

None of the loads on that fuse circuit have anything to do with any of the ignition circuits so the most likely cause is a power short in a harness or under/behind the fuse center. I am not thinking fuse panel because none of the ignition fuses are in that IP fuse panel. That leaves the wire harness from the IP panel towards the ignition column which unfortunately is behind the dash although you may be able to get a look from under the dash at the pedals. Maybe there is some harness damage from the sagging door perhaps near some sharp metal. There are some rare possibilities due to a faulty ground but its going to take me a minute to analyze the common grounds to see if that's possible.

George

 

That's awesome information, thanks man. I've had a bunch of people in other forums tell me to replace the ignition switch before I even attempt to look any further... so I picked one up this morning. I'll get it installed tomorrow and go from there. I think my next step after that will be testing the wires in the door harness.

 

If you dont find a short to power then we can explore the grounds.

George

 

Spent several hours today workingworking jimmy. Replaced the ignition switch, no difference. It doesn't look like its ever had any sort of alarm or anything added, all of the under dash harnesses look to be untouched OEM. Hopefully tomorrow I can pull the door panel and go thru the wiring in the drivers door/door jamb.

 

UPDATE! I found the culprit. The drivers power seat harness has shorted, and melted pretty badly. Gonna spend the weekend scouring junkyards to see if I can find one.

If anyone has a parts truck that had power seats, and would be willing to chop the harness, please let me know!

 

Nice find! Another option is to splice new wires in across the puckered up section but in order to do it properly you need to solder and shrink wrap. Let me know if you’d like some pointers on how to do that and I’ll be glad to help. George