This only happens when on a long road trip and after driving for a while:

With the A/C on full blast, the blower motor will gradually slow down to almost nothing. The cold air is still coming out, but the volume of air is almost nothing.

I can then turn off the A/C, and in a few minutes, the blower motor will start blowing again at full blast. Then, I can turn the A/C back on, and it will work normally for a while, then repeat the whole process.

Is this a symptom of the blower motor resistor or the motor itself ? Or could it be something else ?

Thanks For Any Advice

 

Anybody ?