Chrysler Repair: 94 Dakota Sport lighting failures, dodge dakota sport, 30 amp fuse

Question
I have a 94 Dodge Dakota Sport ext. cab with 3.9L Magnum.  I'll be driving down the road when my dash lights, tail lights and parking lights will go out.  The green 30 Amp  fuse under the dash keeps blowing.  Sometimes I can pop a new fuse in and it will be OK for a day or two --sometimes only a few minutes before it blows again.  Ususally the circuit will fail if I hit a big bump in the road, but sometimes it will simply go out while cruising smoothly on the interstate. This last time, I took the old one out and tried to put a new one in and it blew instantly,(blue spark and heard it pop)  When I turn my hazards on at night in traffic after the fuse blows, my taillights and parking lights still work, so I'm guessing the problem is in the instrument lights?  All of the dash lights except for the one behind the climate controls are working.  Not sure if that particular bulb is burned out or what. The previous owner apparently installed -- then totally removed -- an aftermarket sound system, so I found several mystery wires under the dash area that had been simply chopped off, but none of them seem live.  My mechanic thought that all this tinkering with the sound system may have somehow affected the lighting circuit.  I would like to repair this on my own since I am proficient with wiring and know how to use a volt meter.  However, I don't have an owners manual or a fuse chart.  Would it help to get a Chilton's manual or something similar?  Are there places I can check for continuity?  Will I have to take the whole dash apart?  Also, for what it's worth, the license plate lamps on the same circuit were both burned out and black when I removed them, but the fuse is still blowing without any bulbs in that part of the circuit. Thanks!

Answer
Hi Adam,
Thanks for the detailed history. Unfortunately I haven't attempted to become expert in the line of pick-up trucks so I don't have any manuals to refer to. I think that with a meter that has an ohm (resistance) function and a wiring diagram that you will be able to locate the short that is blowing the fuse. It may be a bulb or bulb holder or it could be a wire with a tear in its insulation so that the conductor is touching the chassis. Once you have the wiring diagram you could locate access to points where you can separate the various branches that are being supplied by that fuse and test each branch for its resistance to ground reading and focus your attention on finding that branch which reads 0 ohms. You may have to have a helper watch the meter while you shake each harness wire and splice areas and bulb holders that are on each chain until you locate one where the meter reading drops to 0 momentarily, because this sounds to be intermittant rather than a constant short to ground. In my experience, the best manual would of course be the one from Chrysler, but if you can't find that one on eBay (Search: Dodge Dakota Manual) for your year of vehicle then try to get the Haynes manual instead which I prefer over the Chilton. In all likelihood the Haynes manual will show the external lighting circuits. You would simply put one lead of the ohmmeter on chassis shiny metal (ground) and the other on the downstream side of the 30 amp fuse socket to begin the search (It should read something above 0.5 ohms (assuming that it reads 0 ohms when you touch the two leads together when you first turn it on) when you have the headlamp switch in the park position (that would represent a draw of 24 or less amps which means the fuse wouldn't blow). Then you have to try and get the resistance to drop to near 0 ohms by means of manipulating all the possible wires that are in the circuit and then examine closely where there might be a short in that wire.
Roland
PS. I would suggest that you begin at the radio harness  which has been disturbed previously and try shaking all those wires while watching the resistance on the downstream side of the fuse socket (the side that has no volts on it when the fuse is removed) to see if you can cause a short to ground reading. The radio illumination wire is on that fuse, along with the dash lights, so it could very well be the location of your short. It would be an orange color wire. Have the headlamp switch in the park position, of course.