You make a good point. I haven't plugged the duct after the fan to see if the head recognizes a parameter that would shut down the system (compressor then fan), have you? A new fan resistor may fix this, maybe not. You and I both know this system is complicated and controlled by a control head (a lot of if this then that, OR if that then this). Fan position 1 does move air albeit at the lowest setting of the system capability. Since this is a new to him purchase AND the resistor is in the same position AND the filter is a maintenance item, why not check to see if a filter is there or totally plugged up? The OP mentioned some have mentioned having a plugged filter could cause this. I have seen airflow problems causing HVAC compressors to cycle and shut down the blower (Not in the crossfire but engineers love to complicate things and the manual doesn't get into the guts of the design of the system). Going along with that (and not knowing if a high pressure situation can cut the compressor THEN the fan within the head settings), is why I suggested he check the filter and if missing, the evap coil. I made no mention of a certainty, just helping the OP find, check, see if one is there and replace his filter before buying a blower resistor.

Before I posted I perused the entire HVAC system in my hard copy of the service manual to see if the refrigerant pressure switch is a high/low design and or on/off switching function, as you know the manuals aren't the most comprehensive and most certainly doesn't give a detailed design criteria. One more note, the fan potentiometer in the A/C head has failed before (erratic), and has a fix in the forum (I did the fix and it fixed my erratic fan operation). I didn't mention this YET because at least the basics should be checked and eliminated before spending money. Thanks for your input.


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