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Ignition-off draw fuse #16 blows

HeepSpeed

NAXJA Forum User
So I've discovered that while the previous owner's mechanic knew absolutely 0 about wiring (the rewired AC doesn't work). Upon looking at fuses to fix the non working gauge cluster and radio, I've noticed that fuse #16 (Underhood lamp, transmission control module, radio & interior lights Looking down at PDC from front of vehicle: Bottom right mini fuse is #16.) under the hood is missing.

Whenever I stick a new one in, it immediately blows. Something is shorting it...any ideas? I'm electrically incompetent but willing to learn!
 
Try the basic stuff first, disconnect as many of the components as you can and add them back into the circuit until the fuse blows.

Look at as much of the wiring as you can and see if there is any obvious damage. Sounds like a hot wire is touching something it shouldn't.

Having been through a similar experience with my 1990 I found the switch in the passenger side visor was bad causing the battery to drain over several days. I found it by breaking the circuit up into sections and checking everything from the component to the fuse until I found it.

If you can get a self powered test light this will be a lot easier.
Disconnect both battery cables, remove the fuse, ground the connector on the probe, touch the probe to the connector that carries the power, if the light illuminates you've found the problem. This will not tell you if the component itself is bad only the wiring.
 
According to his profile, Heepspeed has a '96. Please state year to help diagnostics. Disconnect pieces run from fuse 16, replace fuse and plug items in one by one until it blows. If it blows without anything plugged in, start chasing wiring.
 
oh, yea, sorry about my profile - I have two Jeeps now...I just adopted a 1997 for free...now we know why it was free besides the non-running aspect which I fixed.

It sounds like I just have to trace down the wires that connect to fuse 16? Man, I should take a photo of this weirdness! I know I can do it! I MUST learn! So I'll get a tester and see where that leads me...right?
 
ok, quick update - the lights on the dash work and the lights that go off for the battery, oil etc symbols light up; just not the speedo/odo/gas gauge. When you turn the radio on, you can hear power go to the speakers but the head unit doesn't power on. Don't know if that's helpful and I won't have time to get to the Jeep until tonight after work.

as for unplugging things that connect to fuse 16 (for example the radio - do I pull out the radio and unplug the hot wires to it and then try the fuse or how should I 'disconnect it' from fuse 16?)
 
I would unplug the underhood light, and pull the radio out and see what happens with the fuse. If the fuse doesn't go that MAY mean the problem lies with one or the other of the components. I would lean towards the radio if it is aftermarket and everything else is unmolested by the PO. If there are signs of creative wiring....
 
Yea, unplug the hot wires and retest with fuse. You can also unplug all the stuff and test with the meter, set on ohms. If meter shows you have continuity from the fuse plug to ground, you have a short in the wire. No point to waste a fuse. One other point from my past hard learned experience: only use name brand fuses. I had some cheepos from the dollar store which only half melted and burned a wire and half melted my fuse box. Never again.
 
ok, everything is stock...just creative wiring of the AC, which is wired to a toggle switch inside the car bypassing the fuse boxes, probably because they were too lazy to do the search I'm going to do :(

I'll report back when I find out the results of this unplugging test. It's nice because the dome light is missing, and there is no underhood lamp. Just radio and Transmission Control Module which I'll search out a schematic on where that is. Thanks!
 
also try a company called alldata. for a fee, they can provide wiring diagrams for the iod fuse. that way you can tell exactly what is on that circuit.
 
SO an update. I have the wiring diagrams and have had help on the forums and using the search feature; however, I'm still stuck.

I unplugged everything that draws from fuse #16 in the PDC. Still pops. Dang - must be a short.

I then unplugged the pink wire from the junction box on the other side of the engine. Still pops. wtf? Is the short from the PDC to the junction box? The bundle of cables looks sturdy and shows no sign of deterioration.

My last thought that I JUST thought of it that maybe the PDC ground to fuse #16 is bad? Is that possible? How do I access it? It seems absurd for it to keep popping even when it only goes 5 feet to the other side of the engine bay to the junction box.

Thoughts? HELP? I'm tempted to cut the pink wire on both ends and splice in a new wire to see if that'll work...
 
A fuse is an in-line breaker for a power circuit--it doesn't have a ground.
 
Well, you obviously have a hot lead to one side of that fuse, and that when you put in a fuse it blows, that indicates a short. The short could be a wire with bad/burnt insulation or it could be in one of the components attached to that circuit.

Now, you don't have an underhood light, no auto trans, you have completely disconnected the radio harness, and diconnected the overhead console?

What about the interior light switches, as in the doors? I would start chasing those wires and checking the switches for shorts.
 
Please compare the 96 to the 97 PDC.

On my 96 #16 is a blank. There are 6 minis, from front of vehicle - 3 left row +F19, F20, F21 right row- blank, F17, F18. The PDC F19 goes to hood light and to fuse panel dr. side inside to F9 then to bunch of places including domes, radio etc.

Caution Use ONLY a V.O.M (volt-ohm-meter) for testing. (test lights can damage PCM =$$$)

Good Luck,
O
 
Thanks Orange - the Jeep I'm working on is a 1997. I also have a 1996 (posted in profile so it's confusing, I know).

@Joe: I've disconnected radio, gauges, both door switches, dome light, cargo hatch switch. Pretty much everything I saw in the diagrams that fuse 16 connects to.

I also disconnected the pink incoming wire from the junction box (which I thought would disconnect the wire from going inside the cab?) and it still blows.

Chasing wires means cutting open the harnesses, right? (sigh)
 
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