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Ignition Switch Melting....

KinesthesiaDrums

KinesthesiaDrums

NAXJA Forum User
Location
Minot, ND
alrighty guys...heres one for you to figure out for me....i attempted searching but found nothing.
i have a 1990 Cherokee Loredo, 4L I-6, 2wd, 4door, tilt steering wheel.

my problem is in the ignition switch that is mounted under the dash on the top side of the steering column. this is the 3rd time ive had this swtich go bad in some way within the past year. the first time was mainly due to old age, the contacts to the accessory power power lead were corroded so i would randomly lose power to radio, air, blinkers, whipers...i could wiggle the key and get contact back......so i replaced it...no biggie...
then about 2 months ago i noticed the key started kinda sticking when i would go to turn it off. like the slider was catching on something. then one afternoon it wouldn't turn back to shut the engine off at all....so i forced it, and SNAP! it shut the engine off....everything still worked after that except my accessories...again... so i replaced the switch...again.

so...im driving back down to florida from tennessee this past weekend, got about to Macon, GA and my radio and ac cuts out....after the few "wtf's" i managed to bump the wire harnesses under the dash with my foot and power blipped on, and went back out.....
i proceeded to stop at the next exit and inspect, and hopefully be able to fix this problem....from all i could tell at this point was the brown 12ga wire coming out of the switch (power to accessories....) seemed to not be making contact with the tabs on the switch......so i figured...well, the wires are old..must have gotten corroded...figures. so i rode the next 5 ours or so with no radio, no air, no blinkers, and when it started to rain...no whipers...

well...today i got the chance to tear under the dash and see wtf went wrong this time....after much deliberation and frustration....i pulled the switch out to inspect it..... i was losing current flow IN the switch..all my contacts on the outside were fine... so i opened the switch up to find that the brass tab that connects with the Acc. power wire had actually melted the plastic around it. this reminded me that the previous 2 switches also looked a little toasted, as does the plug that plugs into this switch....but JUST on this brown Acc. wire.
so...after looking over the switch and figuring out how the thing works....i discovered how i lost power. the slider that moves back and forth in this switch has spring loaded "bars" in it that keep pressure on the wire tabs....to keep better connection or whatever...so when the Acc. wire lead got the surrounding plastic hot enough, these spring loaded "bars" pushed the tab out of the switch, through the plastic...breaking contact....
here are pictures of what i saw when i opened up this bad boy:

Inside, the melted tab-
http://img.photobucket.com/albums/v377/darkkittenskaos/Jeep/DSCF1354.jpg
inside, another view of melted tab-
http://img.photobucket.com/albums/v377/darkkittenskaos/Jeep/DSCF1353.jpg
outside, melted tab-
http://img.photobucket.com/albums/v377/darkkittenskaos/Jeep/DSCF1355.jpg
the spring loaded sliders-
http://img.photobucket.com/albums/v377/darkkittenskaos/Jeep/DSCF1356.jpg

soooo...my question to you all.....has this ever happened to anyone? is there some fix, or mod i can do to this switch to make it work again and NOT melt again? i'd like to know if there's a better alternative than buying another one and replacing it every 2 or 3 months....
thanks in advance...
 
To me, it looks like you have too much current draw on that wire. That's what is making it overheat and melt the plastic. You need to determin how many amps are being drawn by that circuit. and the figure out what accessoy is causing the problem.
 
hmm...thats kinda what i figured.....but im not sure where to start for searching what could be causing the excessive amperage draw...and if i did find something...how would i fix it?
i'll see if i can't check how many amps it's pullin tomorrow, im through for the night as of now....how many amps SHOULD it be pulling?
 
Last time mine did that, it turned out that the problem was an intermitent short in the hvac switch. I found THAT out when it finally caught fire. Talk about a booger to put out before the whole thing went up. I would test all the wires and the hvac panel for resistance.
 
i see....i have had kinda low voltages ever since i got this jeep. if i have EVERYTHING off the gauge reads a little under 14. but if i turn the blower on, voltage drops significantly....if i have it on high, voltage is down to the lower line...i think 9volts? my head lights used to drag it down somemore...but i recently converted to an HID system so that doesn't really happen anymore...

could this excessive voltage drop possibly be related with my original problem here???
 
It could be related... I've never seen this happen in a Jeep or even a regular truck... My dad is a big diesel mechanic. I remember a while back he had a bunch of trucks in his fleet that had something simular happen. Turns out the current was wrong when the switch was orginally designed. But that was happening on a few of his trucks all the same year. My thought is have you added anything to your vechicle that runs on the accessory circuit or have something on the circuit that for just draws too much current... I put and xm radio reciever in my XJ that runs off the accessory circuit... It draws a great deal of power... So much that I went out and got the $100 cable so I could use my XM Ready Head unit with it, using the cable would tell the unit to turn off when I wasn't in XM mode on the head unit. Where as before it would stay on all the time. If you have something installed that runs off the accessory circuit that is causing this, I would rewiring it out of the accessory circuit. I would wiring it right to the battery with an inline fuse and run if off a relay that would run off the accessory circuit. Much like fog lights do...
 
the only thing ive "added" to the acc. circuit is just an after market headunit....its a 7" Moniter with DVD player....*grins* BUT...it takes power from more than one place....the factory radio harness on the moniter...and the brain part that i have behind the back seat draws power from my 4ga wiring i have going back to my other stereo stuff in the back, directly from the battery.
but it's not rated to draw any more power from the stock radio harness than the stock radio........
 
is your jeep canadian? if it is, it should have running lights. this might be it. i had my ignition wires replaced under warrenty a while ago, for getting fried.
 
I'd be replacing the plastic connector housing and all the wire terminals. I bet that's all the problem is, poor connection causing heat through resistance, which then multiplies on itself until parts melt or burn.

In reply to a post above: a resistance check on a wire will tell you absolutely nothing about whether it is able to carry a lot of current. Case in point.. a ground cable with all the strands broken but one. A multimeter will show low resistance, so the cable is OK, right? Wrong.. try and pull current through one strand, it won't happen. Extreme example, but makes the point. Voltage drop is the proper test for circuit problems.

Voltage drop: an example would be setting your multimeter to the 20VDC scale and putting one probe on the positive battery terminal and the other on the positive cable lug, 1/4 inch away. Now energize the circuit (starter cranking) and you shouldn't read more than .1 volt. If you had say 3 volts, that is the difference between the two that a bad battery connection is eating up, leaving only 9 volts for the starter.

Now take this idea and use it through the suspect circuit that's using the ignition switch connector. There should be no more than .5 volt drop across that connector. More than that is a poor connection, and heating the connector up.
 
KinesthesiaDrums said:
i see....i have had kinda low voltages ever since i got this jeep. if i have EVERYTHING off the gauge reads a little under 14. but if i turn the blower on, voltage drops significantly....if i have it on high, voltage is down to the lower line...i think 9volts? my head lights used to drag it down somemore...but i recently converted to an HID system so that doesn't really happen anymore...

could this excessive voltage drop possibly be related with my original problem here???
Click to expand...

Mine did the same thing, brown wire got hot. Voltage drops when turning on headlights or A/C.

Have you fixed it? If so what did you do to fix it?
 
randy57 said:
Mine did the same thing, brown wire got hot. Voltage drops when turning on headlights or A/C.

Have you fixed it? If so what did you do to fix it?
Click to expand...

You might take notice that he hasn't been on in over 5yrs.

I would begin by taking current draws to see why you have so much of a load.
 
randy57 said:
Mine did the same thing, brown wire got hot. Voltage drops when turning on headlights or A/C.

Have you fixed it? If so what did you do to fix it?
Click to expand...


Don't know if this will help but one of the "mods" I found on this forum years ago was to install a relay for the headlights. This approach ties the high current device (headlights) to the battery through the relay so the only power coming in/out of the cab is the small current necessary to trigger the relay. There was actually a complete kit available to do this that included the relay, the new wires and all the connectors so it was very "plug and play".
 
You replace the ignition switch and repair the plug, making sure the brown wire is connected very snug.
If it's an 84 to 90, do the blower ground mod in the Tip linked above.

There's nothing wrong with trimming the plastic on the plug and attaching the brown wire by itself either. That way you can verify the connection.

It's a GM switch and they had the same issues in their cars. They overloaded the "ignition on" circuit. the circuit is just adequate, but if it gets any extra load, the switch gets hot and slowly melts over time.

tjmotter, that's why the headlight supplemental harness came about. Same principle, but just on the headlight circuit. The harness is a "must do" and it's easy as pie. I'll include a link below with instructions and a place to buy one for under $20.

http://cruiser54.com/?p=115
 
Improving the ground to the blower will also improve the current it can draw through the ignition switch. :}



I like doing the headlight relay setup on the Renix as well, because it eliminates the voltage drop through the undersized wiring and melt-prone headlight switch. You have to if you want to put in higher current headlights,although now that LED headlights have improved, going LED is an option too.
 
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