furnace fan

What would cause a furnance fan all of a sudden not to run when switched over to on all the time vs when switched to auto. This is a rheem 90+ furnance that was working great until a few days ago.
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Bad thermostat, broken thermostat wiring, or bad blower relay. Call a qualified HVAC company.

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patliz1 wrote:

The only thing I can see would be the switch. A quick test with a meter could verify it. Now the other way around when it would not work on auto, would be more complex as it would include the thermostat or timer whichever was in the auto circuit.
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Joseph Meehan

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