Azrial

I have 1996 Grand Cherokee ignition fuse that keeps blowing at random times. It may take hours or it may take weeks. I have read that this may be caused by a wire from one of the O2 sensors that is shorting aganst something, but I really have no idea and would appresheate any input.

I am also looking for a User Manual for the vehicle if someone can point me in the right direction.

Bustedback

Sometimes the wiring to the O2 sensor will get too close to the exhaust manifold and melt the insulation off of the wire and short it out.

Azrial

So I have read over the last 4 hours, but physically where is the ignition fuse located? I have never been the one to have to replace it!

Bustedback

In the PDC (under hood fuse box), it may be marked as the ECM or PCM fuse.

Azrial

Well we traced out the leads from the O2 sensors from the CatCon, over the transmission and forward to the engine compartment. We could find no shorts.

I spoke to the previous owner who told me that he strongly believes that the sickly green mini fuse in the PDC is the fuse that keeps blowing. I have maked it with a green and white arrow in the photo. He said it started to occur after he was on a trip and plugged in an DC-AC inverter to run his PC. Any more ideas?

dave1123

Can you tell by looking at the fuse if it's an overload or short? If it's on overload, you'll see the ends just melted. If it's a short, there will be metal blasted away and blackened.

Azrial

Well as soon as it blows this fuse for me, I will take a look at that! I am just being proactive here. This was a consistent problem for the last owner and as I am now recovering from a severe accident, I am a little nervous about riding in a vehicle that could lose all power at a moments notice, like getting on the on-ramp to the interstate...

But, on seeing the different types of fuse damage, what should I assume. I am not following your diagnostic reasoning here.

Thanks!

mxpxpunkrock1987

i would replace the wire harness if the o2 sensor area is or has been melted and go from there its not hard

Azrial

Thanks, I have considered replacing the whole wiring harness, but the O2 wires forward look great and are very securely mounted to the frame forward to the engine bay. I would honestly have to say that they are in good shape.

As apparently these problems started for the previous owner after plugging in a DC\AC Voltage inverter, I am beginning to suspect that it over loaded the circuit from the cigar lighter and damaged the associated wiring. I am wondering if that is a possibility?

Bustedback

That is where I would start looking. I would not tap into an exsisting circuit for an inverter, it should have its own fused lead directly off of the battery.

dave1123

Amen, brother. Inverters tend to draw lots of amps.

Azrial

Oh, I agree. In any vehicle I have run any inverter over 75 amps, I have wired it directly to the battery with its on fuse. But sadly, this one was plugged directly into the cigarette lighter. I will see how well I can trace this circuit. This has been a bit problematic as I am going to be on crutches for a few more months.

dave1123

Did he use the cigarette lighter socket or the power outlet? They are on different circuits and fused separetly. If he used the cigarette lighter, some plugs can damage the contacts inside. Maybe you've got an intermitent short in the socket. The power outlet is hot all the time. The cigarette lighter is hot with ignition on.

Azrial

I do not know and at this point, two years later, I guess that it would be hard to tell. But thanks for the information it will be helpful in figuring out the problem.

I have also noticed that the graphic trouble display is inaccurate. It sometimes says that there is trouble with the level of the windshield washer fluid levels and that the rear lights are out. Neither problem is true. The gas level gauge is also wrong sometimes and will show the fuel level at Empty, even though there is plenty of gas in the tank.

NOTE: I guess I should mention that I do not know what the graphic trouble display is really called. I have not been able to locate an Owner's Manual for this vehicle.

dave1123

Go to a junkyard and look through glove boxes. That's how I found mine.