[KF4SQB]

I wonder if this issue actually stems from the electrical contacts on the connectors oxidizing over time, and as a result, its the connectors that get hot and cause all the trouble. One poster said that he's found that people often find that replacing the blower motor doesn't fix the issue. This would point to the contacts at the resistor plug getting hot.

So maybe the solution to preventing a melted resistor plug is simply to clean the contacts at the resistor and apply some anti-oxidant?

There is absolutely oxidation on the connector contacts, and I'm sure it contributes, but, in my opinion, it is a fairly small contribution to the issue to start with. To clarify, the oxidation is caused more by the excessive current being drawn, than the excessive current is caused by the oxidation. People have failed to correct the issue by replacing the motor because damage has already been done to other parts of the system. Go back and carefully re-read what I posted before about this. You do add a good point, as I didn't mention oxidation before, but I pretty well cover the issue above. The oxidation issue falls right in line with the connectors mechanically failing due to heat, and occurs at pretty much the same rate, as heat speeds up oxidation. To give a bit more perspective, I'll give a basic explanation of how the various measurements of electricity interact, and compare them to water flow in a pipe. Electricity is measured in "electromotive force" (more commonly referred to as voltage, or volts, and measured in volts, analogous to pressure), "resistance" (commonly measured in Ohms, analogous to a restriction like a globe valve that can be used to precisely control flow), "intensity" (more commonly referred to as current or amperage, measured in amps, analogous to flow rate), and "power" (more commonly referred to and measured in watts, this is a measurement of work done, in the form of the light put out by a bulb, or the rotation of a water sprinkler). The relationship between them is expressed as Ohm's law (E=I*R), and Watt's law (P=I*E). So, if you measure current ("I") and resistance ("R") in a circuit, and multiply them together, you will get the voltage ("E"). By the same token, if you calculate E/R, it will give you amperage, and E/I will give you resistance. Similarly, P/I=voltage, P/E=current, etc. With this in mind, with any two of these measurements, the remaining two can be calculated. If you perform the calculations, you will see that as voltage goes down, current goes up, if the load (resistance) doesn't change. If the load does change to a higher resistance, this will cause the voltage to drop, and, you guessed it, the current to go up. As aging components go up in resistance, meaning they don't allow as much voltage to pass through anymore, that means that there is a lower voltage, which, you guessed it, causes the current to go up. Higher current=more heat=more damage=more resistance=higher current=more heat=more damage, lather, rinse, repeat. It's an ugly cycle. So, yes, oxidation on the connectors causes higher resistance, but higher current causing more heat is what starts the oxidation in the first place, so simply keeping the connectors clean will only prolong the inevitable.