Ignition smoking

[rm2406]

HELLO ALL, I am wondering if anyone has an idea what might cause ignition wire harness on steering column to get very hot and smoke when and only when AC is on?? It's not always but it does happen from time to time..is it possible the contacts on harness that plugs into the key module need contact cleaner or ? other than AC on causing it to get hot its fine

[Brasscatz]

Hmm, sounds like there could be a short in there. Definitely not something to mess around with though

Sent from my Samsung Galaxy S4 because my microwave couldn't do it

[Mudderoy]

HELLO ALL, I am wondering if anyone has an idea what might cause ignition wire harness on steering column to get very hot and smoke when and only when AC is on?? It's not always but it does happen from time to time..is it possible the contacts on harness that plugs into the key module need contact cleaner or ? other than AC on causing it to get hot its fine

Yep like Brass was saying, I bet there's an electrical short somewhere, or there is a component that is bad and sucking a lot of current.

Have you made any recent electrical or mechanical changes?

[rm2406]

no changes to ignition or electrical.. my last cherokee the AC was not working but when i changed out the ignition module the same wires that get hot on my current jeep are the same that were almost totally burned up on my last jeep.. well yesterday when i was driving i noticed a little smoke coming from the key module(also the AC on) so i pulled over and opened up the column and felt the 2 wires (red,purple) very hot to touch some what smoldering.. so i turned off ignition and it looks like i turned it off on time before damamge was done to wires.. when they cooled down i pulled the harness off and i noticed what looks like some kind of yellowish grease (not thick very liquid-dee) my last jeep also had the same color grease in there??? there is almost no way for anything to get into harness at connector as its segregated housing.. so i blew the connectors out with air until no more greasy liquid came out.. started car and turned on AC and let it run for 10 mins.. so far no smoking.. from what ive googled there are TONS of this problem with cherokees but no solutions.. just curious if anyone else here experienced it???

[rm2406]

UPDATE: changed out key tumbler and no more smoking steering column.. after inspecting the bad tumbler and good tumbler side by side i noticed they use a grease inside to keep the key switch mechanism moving freely but after awhile the grease seeps down into the harness causing the wires to make somewhat contact, then heats up and eventually starts smoking and also KILLS the ac/heater control switch!! ive checked other cherokee at the yard and the ignition harness that connects to the tumbler ALL had a burnt look to them and also were semi greasy.. just thought id share my experience in this situation...

[NW99XJ]

To me it sounds like the grease in the ignition was NOT dielectric grease, if it was, there would not be a short.
The Red wire in the ignition harness is the constant power...this wire is always hot.
The purple is the accessory wire. This wire only goes hot when the key is turned to the first position, or in some cases, in the backwards position (turning the key back towards you past the off position.)
This wire controls power to the PDC (power distribution center) and feeds the circuits like radio, heater/ac/fan, etc....
Even if these two wires were to short together, it wouldn't be an issue....but it sounds like they (or rather their contacts inside the tumbler) shorter or at least partially shorted to ground thru the moisture in the grease. Dielectric grease is non-conductive, and would not have caused this issue.
Now that all the "hind-sight" is out of the way, lets focus on your solution.....
blowing the ignition module/tumbler out and getting it all nice and clean is a good start. Swapping it out probably wasn't all that necessary, depending on how much damage was already caused by the shorts. In any case, I would highly recommend putting some dielectric grease into the replacement tumbler. This will not only keep things operating smoothly, but will ward off moisture, corrosion, and will prevent any future shorts.
I would also do a really thorough examination of as much of the wiring as you can.... tracing the wires that were the hottest and replacing burnt sections, or at the very least wrapping them with an insulator of sorts. (electrical tape will work ok for this)
Also look closely at the fuses in the fuse blocks. The affected circuits may have gotten hot and the terminals may have melted some of the plastic surrounding them in the fuse block. Replace any melted or corroded fuses immediately.
Bottom line? .....glad you got it fixed, and good job on being diligent about your troubleshooting and subsequent repairs!