First, thanks to all who have offered their diagnostic advice... I have narrowed down the problem, I believe, to either the heater blower motor or the heater fan motor resistor. I obtained a used heater fan and motor out of a wrecking yard and tested the fan motor by applying 12VDC. It worked fine. I also obtained the compnanion heater fan motor resistor for our automated ECC (Environmental Control Module). The automated version has a resistor that has an aluminum-finned heat sink while the manual ECC version is ceramic. I have the former. My one remaining question is how can one test the resistor outside of the vehicle to ensure that it is good? I tried to measure the ohmic resistance with a simple DVM but got no reading. Is this a conventional resistor or is it a MOSFET chip or some other type of device?
Any guidance will be greatly appreciated as I will attempt to fix our malfunctioning heater blower shortly.
Many thanks,
OnlyVolvo
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