Furnace fan (blower) will not shut off

[dj1100rt]

I have a Heil, gas, condensor furnace. The blower stays on forever after a heat cycle. Model #NUGK100DH3. Unit is a 1989 model.  I replaced the fan relay today and the problem persists.  I have the same problem after an air conditioning, cooling cycle: the fan stays on all day long after a cooling cycle.

What's a good next move?

Thanks,

Dave

[RegUS_PatOff]

Is there a FAN/AUTO Switch on the Thermostat ?

How's the Control, fan and limit # 16 (top right side)

[dj1100rt]

The fan auto switch is set to auto.  Is there a test for the fan limit/control?  I have an ohm meter.

[RegUS_PatOff]

 

This Fan and Limit Control has a 6 wire hook-up

2 wires are the Fan Switch,

2 wires are the Limit Switch

and the other two wires are the Time Delay side of the Switch.

 

 

[applianceman18007260692]

If the unit is off and the furnace is cold then the  FAN portion of that FAN/LIMIT should have no continuity. The dial that goes around as the bi-metal heats up may be stuck in the on position.