TL;DR: That's not how PPTC's are used and wouldn't account for this fault.
It's very unlikely to be a PPTC resettable fuse for a number of reasons. PPTC's are used in circuits where there is an extreme state/abuse, a last ditch effort to save the device. They do not trip in the normal operation of the device and have to be rated for a temperature fairly high above the normal operating state.
Otherwise, you'd have extremely delayed protection from it in winter yet it would always trip in summer because of the temperature difference. A motor in a stalled state just wouldn't build up heat THAT fast to operate as a window stop.
Further, they cannot withstand constant operating cycles, have a fairly limited number of resets possible, lower than a window circuit would need. Their specs can tell you a wildly high # for # of resets possible but this is repetitive in a lab environment rather than exposed to a real world circuit where they receive thermal cycling constantly, even without tripping, and cannot be used as a stop limit for a highly repetitive circuit state.
When one blows, it continues to pass a
hold current and typically will not reset until power is disconnected from the circuit and several seconds pass for it to cool down. This is not the operation seen in windows where the user may put it all the way up and right away want it back down, so it is doubtful that any auto manufacturer would use one as a stop limit for window travel even if any of the other factors wasn't present.
Plus, if one fails it practically always fails to an open circuit state which would mean if the theory of stopping the motor at the end of travel by a PPTC was plausible, a failure of the PPTC would mean the motor no longer works at all. It's not impossible for the thermal activation range to drift or for it to have a delayed response to thermal changes, but usually the user would never notice this as these ranges are set so high above normal operating temperature.
That's just not how PPTC's are used in circuits. They are only to stop operation from a fault. That fault could be user input, holding a window switch down and keeping it help down till a motor overheated, but for the reasons stated above, that's not related to the fault rasouth is observing.
Lastly, PPTC failure is fairly predictable and we would be seeing many different 2nd gen Explorer owners having the same failure by now, so much so that it could be called "like clockwork" or a "wear item".
If anyone is interested, here is an Application Note linked below for how to best implement PPTC's in a window circuit, and it's not in the motor, rather an area that does not experience significant thermal changes like a motor would every time it operates. That may seem counter-intuitive but comes back to the reliability of the polyswitch when exposed to equipment operating state temperature changes, and protects against other overcurrent events besides just a stalled motor such as a short circuit in wiring, relay, or switch (or transistor or other in newer more sophisticated circuits than our ~20 y/o vehicles have):
https://www.littelfuse.com/~/media/...trol_switch_consoles_application_note.pdf.pdf
I'm not suggesting that window motors don't have PPTC's in them. Some definitely do, but are not meant to trip at all and would not account for the problem stated in this topic.
If you want to use a thermal limiter for high cycle count circuits, use a bimetallic switch if it must be passive, to avoid the increased cost and complexity of active temperature feedback for a microcontroller... but it still wouldn't work for an end-of-travel limiter on a window, the response time is still
way too slow.
