You were absolutely correct about the voltage. I wrapped the common wire an extra time in the sensor loop and it added an extra 2 volts. So, at full speed the sensor puts out around 4.5 VDC. I was able to get both, the opto-isolated and AN1 as a digital working without configuring the voltage endpoints. (default setting is appropriate for my situation)
I removed the 1M resistor because it didn’t make any difference. Any ideas why a resistor would be recommended since the CRmagnetic sensor is totally isolated from the current of the air conditioning unit? Is it to prevent interference with the other inputs?
Thanks for your help.