Chrysler Repair: IOD Fuse 1999 Durango, fuse box, metal chassis

Question
Hello,  We keep blowing the IOD fuse in our 1999 Durango SLT Plua 4x4.  It blows on contact when you try to replace it.  We just had a new transmission put in the vehicle and the fuse started blowing after that.  The dealer wants to charge us an arm and a leg to investigate after we've already been charged approx $4,100 for the transmission work.  Therefore, we don't want to take it back to them since we can't afford to spend anymore money on this right now.

Is there anything to do with the new transmission that could be causing the IOD fuse to blow.  It had never gone out before now.

Thank you so much,

Cathy

Answer
Hi Cathy,
I don't have a Durango manual but I checked the mininvan manual to see whether there is any IOD current supplied to the transmission computer. The ignition off draw (IOD) fuse (I assume that the fuse in question is labelled IOD) does not apparently provide current to the trans computer or the trans itself. It mainly supplies power for all the courtesy lamps that you expect to be working when the vehicle's ignition switch if in the off position. So I doubt this problem is related to the transmission unless inadvertantly a wire was shorted in the process. The trans computer does draw some current after you turn off the engine, for a few minutes, but that current is not supplied by the IOD fuse.
You could approach this by means of a volt-ohmmeter, measuring the resistance to ground as shown on the side of the fuse socket that in not provided with 12V (what I call the 'downstream side' of the current flow). It would show a resistance of 0 ohms to 'ground' under the present circumstances, where 'ground' is any shiny metal chassis point near the fuse box. Then with the doors closed measure the resistance to see if it still shows 0. If it doesn't then one of the courtesy bulb that normally come on when you open the doors is shorted. If it still show a short then one of the bulbs that are actuated by a different action (opening the glove box, turning on a vanity mirror light, etc. is a more likely cause and you should try removing those bulbs one at a time (still with the doors closed). You need to find some bulb which when removed causes the resistance reading to rise noticeably when there are no other bulb circuits are being brought into service. Any bulb when in the circuit will likely cause a resistance of several ohms, so you are looking for a subtle difference between dead short and a few ohms. A few ohms won't blow the fuse but a dead short will.
Roland