The 3rd prong (corresponding to setting 3 on the switch) has fried for a second time, the metal prong is blackened and non-functional.

I put the connector, resistor and motor in just a few months back.

What would cause this and how do I find the root cause?

Thanks!

 

Year?

 

Sorry, its a '97 xj i6 4x4.

 

check your blower switch in the dash. the connector in the back is probably fried. at least if it's a 96 and lower that's my guess. not sure about later models.

edit: just saw you posted right before i did, answering the question about the year. i'd still take a peek in there to make sure.

 

I just took a look and the switch wires don't look burnt up or anything. Anything else I can check?

I was looking at the wiring diagram and it looks like there's a relay... I wonder if it could get stuck in the on position somehow and be sending current all the time?

What else could cause too many amps on that wire/prong??

 

Blower motor may be worn.

 

Blower motor was replaced about a year ago. Could it be bad already? How to check it?

 

Shouldn't be.

Find your blower motor resistor and see if it has crap on it.

 

If by position 3, you mean max blower speed then thats the maximum amount of current through the blower circuitry.
On 97's and up, the relay is energized as soon as the ignition is turned on.
I doubt the relay is the problem but might as well replace it as a PM, they're cheap.

Do the other blower speed positions still work?

Just replacing the burnt connector might not be enough.
Did you inspect the burnt pin with the blower switch's mating pin?
If the switch's pin is also burnt, it'll cause a new connector pin to fail eventually.
High impedance connector contacts can produce enough heat to burn the connector pins even melt the connector itself causing a potential fire hazard.

If the root cause is not a faulty blower motor then i'd suspect the blower switch might need to be replaced.

 

Note from DJ
Here's a diagram by CCKen of the HVAC blower circuit applicable to the '97-'01 XJ.
Blower motor relay location on 12-23-12
https://www.cherokeeforum.com/f2/blo...cation-157686/
Post #10 by CCKen
Here's a diagram that shows the location of the blower relay on the '97-'01 XJ. Roll down the glove box and there she is.

 

When I pulled the resistor out, there was a leaf snugly wrapped around the other side of the 3rd prong/leg of the resistor. It was a slightly charred. Probably culprit?

Fortunately, AZ had a lifetime warranty on it, so I just put a new resistor in for 0 dollars.

BTW, by 3rd prong I mean, counting from left to right as you look at the resistor when its still plugged into the hvac, the third one over to the right. It corresponds to the setting #3 on the switch (I know this because when it was bad, setting 3 didn't work).

I did go ahead and replace the relay, a couple of the legs looked pretty blackened.

Can you guys think of anything else I should check to make sure this doesn't happen again??? I especially don't want to chance a fire.

Thanks.

 

OK, thought you meant the burnt prong was on the heater speed control switch.

Those resistor module elements can get real hot at the lower blower speeds.
If its blower speed setting 3 (medium2), that generates the most heat as it uses only one of the three resistor elements. It can glow red hot.
At the highest blower speed setting all the resistor elements are by-passed allowing the blower motor to get maximum B+ voltage.

Could of been the leaf, a bad resistor module or unlikely debris caught in the squirrel cage causing a motor over current condition since you found that leaf.
More than likely it was corroded or spread connector contacts.
Since you replaced the resistor module and connector and all is working, keep an eye on it.

I replaced my resistor module maybe 10 years ago with a NAPA part. Still working.

 

Be careful of those leafs.......I had one get caught on the resistor in an old ramcharger I had, and the end results was a vehicle fire.....not pretty.

I had nothing to put it out with, as the ex had conveniently removed the fire extinguishers from the truck without my knowledge, so I pulled over to run in the store to get something, and by the time I came out, someone had sprayed dry chemical in thru the cracked window....effectively trashing the whole interior as it put the fire out (which was still contained in the vent ducting at that time.

 

OUCH!!
Thanks for the fire extinguisher reminder, keep forgetting to pick one up.