Heater Circuit Failure Root Cause?

[k1n3k]

I just sorted out the heater in my TJ, I am fairly certain it was a failing motor pulling too much current. It cooked literally everything though... The resistor still needs to be replaced so all the speeds work, the main switch bit the dust, the relay was melted, and the harness was fried in each location. I think the speed selector switch survived according to the multimeter . It looks like that has been replaced once as well as the plug at least, so maybe its fine. The resistor is bad though, only have low low, medium low, and hurricane force.
Regardless, looking over the wiring diagram it seems like everything that got toasted near the switches was on the ground side of the motor, and the relay is on the hot side. Logically it seems that it was a bad motor causing the magic blue smoke to leak out. Are there any other failure modes that can cause this issue that I'm not aware of?

 

[reddvltj]

I just sorted out the heater in my TJ, I am fairly certain it was a failing motor pulling too much current. It cooked literally everything though... The resistor still needs to be replaced so all the speeds work, the main switch bit the dust, the relay was melted, and the harness was fried in each location. I think the speed selector switch survived according to the multimeter . It looks like that has been replaced once as well as the plug at least, so maybe its fine. The resistor is bad though, only have low low, medium low, and hurricane force.
Regardless, looking over the wiring diagram it seems like everything that got toasted near the switches was on the ground side of the motor, and the relay is on the hot side. Logically it seems that it was a bad motor causing the magic blue smoke to leak out. Are there any other failure modes that can cause this issue that I'm not aware of?

You pretty much nailed it. The subject has been discussed ad nausium in multiple threads on the forum. Ultimately the fan is the failure point even though you can replace all the other components and get everything working like "new" it's only a matter of time before the fan motor drawing too many amps will melt it all down again.