Unrequested excess smoke: melting wire

[hear]

After fixing numerous bare wires in the "under body harness" I finally set out to actually start the Jeep last night. It cranked & cranked & cranked but never would even attempt to catch. Have never had this problem before. Left the key ON to see if I had any new codes while I was contemplating, and was surprised to find smoke coming from the back of the dash, roughly around the area left of the gauge cluster. Upon further inspection I see the pink/green wire (at least I think that's what color it is) shows signs of melting. I'm guessing that's the source. I plan to open up the engine bay section of the harness next to inspect the rest of those wires, but I'm wondering if any other symptoms might point to a specific cause or troubleshooting steps. I should add that while I significantly infiltrated the wiring over the last few days, I never had more than one wire detached at a time so I know I didn't criss-cross anything. I also didn't dig into anything other than what goes to the transmission plugs and the run to the drivers side tail light plug.

With the key ON I see these (new) behaviors:

• no volt meter
• no fuel gauge
• no communication with OBDII port
• I do have the odometer showing my mileage
• I do have other dash lights: airbag, seatbelt, check gauges, turn signals, low fuel, and if I turn on the headlights I get the rest of the cluster lights on. The CEL seems to be missing from the startup cycle, although I have seen the light come on (and I just replaced it with an LED so I'm confident it works).
• if left ON for maybe 15-20 seconds I start seeing smoke as mentioned above.
• At one point it felt like the loom that runs the length of the firewall was hot in the area directly above the PCM. I did not feel anywhere else, and I didn't test this a 2nd time to prove it.
• Fuel pump relay does not click when I turn the ignition to ON. (never had to mess with the fuel pump before, but I believe that is a standard test?)

As it pertains to wiring fixes I just did, since the gut reaction is to assume I screwed something up:

• Car will not turn over in gear, only in P or N
• I have reverse lights now when in R, and not in any other gear
• I changed the speedo plug, can't verify that's working if I can't drive it
• I changed the NSS connector (not at the sensor, but at the connector 12" upstream)
  • It has 3 wires coming from the NSS but 4 wires on the other side of the plug, so the black wire effectively terminates in the connector.
  • FSM suggests that that wire only exists/matters if you have a manual (I have an auto)
  • I left the wire in the loom but taped it off since I used a 3-wire connector.
• I actually wired in the TCC plug

This is sort of diarrhea of the keyboard but I'm trying to capture all my notes in the event some of it makes a light go on for someone.


See the melty pink/green wire. I believe it is the ignition wire but I would love confirmation on that.

 

[Modoc Guy]

It seems like you’ve got a dead short somewhere, but I can’t suggest anything other than checking the wiring diagram in the FSM.

Have you downloaded the one for your year Jeep?

I’m not much on electrical trouble shooting, but I’d be looking at the starting circuit to start with. Provided that burned wire is an ignition wire.

Hopefully a more experienced mechanic will add to the discussion.

 

[macleanflood]

Also possible you're missing a ground...going to have a spend some quality time with the multimeter on continuity and your FSM. Sure hope it's not an early 96 (aka 97) like mine... diagrams so far have not been 100 percent accurate.

-Mac

 

[hear]

Based on things like the hood latch, I think it’s a later 97. I have the FSM, just haven’t gone through this section before.

One thing I don’t have a good handle on is anything that goes through the PCM, and also which things are controlled by it. Like, is the volt meter controlled by the PCM or is it a “direct measurement?”

 

[Jerry Bransford]

Can you get to either end of that pink-green wire and describe what it's connected to? That is key to finding it in the schematics and being able to come up with a possible cause of it burning up. I did a quick scan of the wire colors in the ignition and instrument cluster schematics and haven't yet found a pink-green wire.

 

[hear]

I can’t get there yet, but I have that 99 harness in my garage. I’m going to trace the wire there and see how it’s routed, and then find it on the diagrams. It looks like it goes into the huge tan colored “plug receiver” behind the speaker. I don’t know what that is called or if it has a name. It has 3 rectangular connectors that make up the bundle that goes through the firewall there.

 

[hear]

No success yet...but I think it is actually a green/red wire, or possibly dark green/dark red. These things are subjective. The melted section isn't on the portion that comes through the firewall, it's on the back side of that whole massive connector assembly which is behind the driver's side speaker area.

CALL FOR HELP: if anyone can identify that wire & what circuit it's part of, I would greatly appreciate it. The way the FSM wiring diagrams are structured, it's just about impossible to find any wire if you don't already know its purpose. It's now stuck to the pink/brown wire if that helps.

 

[Jerry Bransford]

I spent way more time than I should have looking unsuccessfully through all the circuits for a green wire with a red tracer. It's there somewhere but looking blindly it not my cup of tea. Please try to trace that wire one way or the other and figure out where it starts or ends.

 

[hear]

Oh wow, I definitely didn’t mean for anyone to plow through the diagram for me! I was hoping somebody would chime in and say “oh yeah, the red/green wire controls the magneto inverter” or whatever.

I’m currently removing the dash (had to run out to get a steering wheel puller), but from what I can currently see It goes into one of the heavily taped sections that goes behind the gauge cluster. I can’t get to those sections yet so I don’t know which path it goes down from there. My *guess* is the ignition cylinder since turning the key on makes it melt, but IDK.

The other end goes into the back side of a massive connector array that holds like 6 wide rectangular plugs. That “connector array” appears to be mounted to a metal bracket that is bolted to the side of the tub with three 8mm bolts.

 

[hear]

I found this pic on another thread here. The wire in question can be seen in the upper left.

Does this whole thing have a name?

 

[hear]

Ok, it’s the heater circuit, F24. The connector is C202.

Also look to have some burning across the section that runs across bottom edge of the windshield behind the dash. Completely baffled how this got introduced based on the stuff I touched, but here we are.

I guess I get to finish removing the steering wheel and dash and start digging into the harness. No amount of troubleshooting will matter if I have known melted wires.

 

[hear]

Ok, finally traced the better portion of this wire. It's the red/light green wire on circuit F12....light green, green, and dark green are all pretty similar in a dark garage. F12 is the circuit for a whole bunch of stuff listed below. Sorry Jerry, for sending you on a wild goose chase on the wrong color. I was on the same goose chase most of the day.

If you're following along at home, it's a 20GA wire and comes from glove box fuse #11 and runs in the big bundle behind the dash to cavity 10 on C106 (one of the six 12 or 14 pin connectors). Then out the firewall and up to splice S102 which is above & before the PCM. That splice is where the magic happens and is zeroing in on the smoking gun (no pun intended).

S102 goes to the following locations:

• Evap/purge solenoid (no symptoms there)
• ASD (don't know enough about this but could be involved)
• Fuel pump relay ==> key ON I'm not hearing or feeling my fuel pump relay click
• Rear window defogger (haven't used it, ever)
• AC clutch relay (A/C has never worked anyway for unrelated reasons)
• DRL Module (I don't have daytime running lights...should I?)
• Connector C103, to splice S131, which goes to
  • PCM connector C150 cavity A2
  • Torque converter solenoid

The TCC wiring was one of the repairs I did last week. I'll be very surprised if I wired that backward, but anything is possible when it's amateur hour out in the garage. Also because some jack wagon at Chrysler decided that the 2 wires going to the TCC needed to be Red/Light Green and Orange/Light Green. Because colors never fade and lighting sources are always pure white, this could never lead to confusion. Seeing these colors in the diagram has me 99.99% convinced that I spliced in that new TCC connector backward. Of course the TCC plug will also fit rotated 180 degrees which should effectively reverse the leads...this section must've been designed by some intern hired by Lee Iacocca's black sheep brother-in-law.

@Chris I can't change the title to this thread, but we should remove "heater" from the title because it ain't the heater and there's no sense in having the title misleading.

 

[hear]

Follow up on this so as not to mislead anyone who encounters this. I did not wire it incorrectly despite the similarity in faded color wiring. What I determined is that if I plug the TCC in with one orientation, it blows the #11 fuse. If I plug it in the other way, the TCC does not blow the fuse and actually works correctly: P0743 clears on it's own and the engine is observed to slightly drop RPM once it engages in 3rd gear.

I had a replacement TCC solenoid that I hot-wired (outside the trans, obviously) and felt it click regardless of the polarity & no fuses blown. This would suggest that (a) the orientation of the plug shouldn't matter and (b) even if I had incorrectly wired it it should have still works. So It would seem that my existing solenoid is somewhat broken, but not so broken that it doesn't do it's job. Next time I have to drop the transmission pan I guess I'll strongly consider changing out that solenoid. But for now, I'm back to 100% running after a host of related wiring fixes.

Pro-tip for all you little leaguers out there: make sure your fuses are correctly sized for the circuit. In my case the smoke/melting was because a 20ga wire in question is only rated at 11A but was on a 20A fuse so the wire melted before the fuse blew. The factory has this on a 10A fuse (which honestly seems too high, 5A might be more appropriate?). This was not the only incorrect fuse I found once I checked them all. Knowing the current draw of your load is every bit as important as knowing the current rating for the wires that supply it.

More on related issues here: https://wranglertjforum.com/threads/more-reverse-light-woes.57912/

 

[InOmaha]

One issue with fuses is previous owners might blow one and stick in whatever they have on hand to get home.

It is a good idea to check them all to make sure they are correct and haven't been switched around over the decades.

 

[hear]

I assume that's what the PO did to initially overcome some of the wiring gremlins. At some point it all broke bad enough that it didn't even short out anymore. Then I fixed all the wiring (but not the solenoid) and I created a new problem that the correct fuse would've covered. Truth is in a fully operational system you could use 100A fuses everywhere; the fuse size only matters the instant something goes wrong. So use what you need to use to get you home, but correct it immediately, because in the extremely likely scenario that something doesn't work right that fuse will save you hours of wiring fixes or a possible fire. I suppose I got lucky that my daughter noticed the smoke right away.

 

[LONGJP2]

Once you let the magic smoke out, it's really hard to get it back in.

 

[freedom_in_4low]

Glad you got it figured out. I love the thread title.

 

[hear]

Once you let the magic smoke out, it's really hard to get it back in.

This was factory smoke. The aftermarket smoke just isn't the same since they moved operations to China.