Inside fan runs continuously even when compressor shuts down

by Jesse
(Evans GA)

A 2.5 ton Lennox split system. Possible 1995 model.

No external thermometer in compressor unit.

Thermostat is a LENNOX Model 21J701

Heating and cooling were both fine until a week ago when the fan stopped shutting off when the heat cycle stopped.

Changing the thermostat switch from AUTO to ON has no effect. Fan stops when the HEAT/AC switch is centered as it should.

Emergency heat works and the fan runs. Space is never warm enough to deactivate emergency heat or shut off the fan.

When the HP is working, the temp change is from 70 ambient to output temps of 84-86

When heat strip is engaged, output air is 91 degrees.

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