Ok, since you know so much about it - and I admit that I do not - what are we supposed to replace? I've been given to understand - rightly or wrongly - that this is just an endemic problem with the design. If its the motor that is drawing too much current, maybe the motor is crap to start with since "they all do that" from what I've been told.I gotta laugh at the thought of trying to "build a better mouse trap". Rather than trying to find a way around replacing the actual cause of hot wires and/or blown resistors, maybe, just maybe replacing the part that actually causes those conditions is the correct solution!
I'm no motor expert but according to my armchair reasoning motors draw more current for more load.
Yes the motor drawing too much amperage is the most common problem. Secondary to that is corroded connections, then deteriorated wiring. Use of substandard replacement parts can add to these issues. If you haven't figured it out yet, the more you dive into repairs and maintenance, Jeep did not do us a whole lot of favors when it comes to the electrical and computer side of our beloved TJs. They are very picky as to what we put in them. OEM, although getting harder and harder to find is, in a lot of instances the only thing that will work properly. especially when it comes to sensors and in this case fan motor.
Interesting thought, too bad TJs didn't come with cabin air filters. Heater core blockage will definitely result in lower velocity air coming out the vents but I don't thing it would impose a higher load on the fan motor. Of course I could be wrong.I'm no motor expert but according to my armchair reasoning motors draw more current for more load.
Watch the systemic problem be everyone's cabin filters are so clogged up it can't move any air without burning up
Actually... Now I want to fish a borescope in there to check out my heater core. Maybe there really is some blockage somewhere...
Filtration might be able to help prolong fan motor life though if you really wanted to dive into that... A cabin air filter would stop a lot of dust from building up on the actual blower. As for the motor itself, being exposed to elements on the outside of the firewall, I'm not sure if there is anything that could be or needs to be sealed from dust/mud? I honestly didn't look that close at mine when I changed it out last fall to see if there were any openings in the motor case. I just vacuumed out the heater box as best I could and replaced motor, resistor, resistor wiring, and fan speed switch.
I'm not trying to argue here but in my case the OEM resistor block failed. Its connector looks really good, although it's the only one I've looked at so far. And I'm not really sure what actually caused its failure. You can see my pictures of it a couple of posts back.
If you're not seeing any signs of wire fatigue (excessive heat) at the plugs, you might just have a faulty resistor, it happens. Now if you keep replacing resistor after resistor and you are using an OEM resistor, then you might have a high amp draw or possibly a poor ground issue.
IMO the biggest issue is they wired and built "to design specs", instead of allowing for a variance. What some people might call overkill. Using "adequate" wiring/circuitry instead of something that would carry more current than the circuit protection allowed for.
Yea - that's what I'm trying to say. You're more eloquent than I am, I babble too much! I was taught to always design in a margin, and it looks like Jeep didn't always do that.
There has been a "better mouse trap" around for a while that some others in the forum have done to combat letting the factory smoke out of the wiring harness. Running a separate relay bank between the switch and the fan, ultimately improving the ground path with heavier wiring. By improving that part of the circuit it drastically reduces the heat at the resistor pack and switches, which is what causes premature burn out of components.
