I have a Trane electrical furnace with a heat pump. Everything was running fine until 2 summers ago I was having an intermittent problem when I ran the cooling. Even when the set temperature was reached the fan would continue running even though the thermostat had the fan "OFF". Actually the fan continues to run even when I have everything turned off on the thermostat. The problem continued last summer but became more frequent until the point where the fan would never turn off no matter what I tried unless I shut off the power to the furnace altogether. This problem has now carried over to the winter even when I have the heat on and the set temperature is reached. In both the cooling and heating setting the heat pump shuts down as it should but it is not followed up with the furnace fan shutting off as it would in the past.
What is the likely problem and the cause?

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Originally Posted by pcampisi

I have a Trane electrical furnace with a heat pump. Everything was running fine until 2 summers ago I was having an intermittent problem when I ran the cooling. Even when the set temperature was reached the fan would continue running even though the thermostat had the fan "OFF". Actually the fan continues to run even when I have everything turned off on the thermostat. The problem continued last summer but became more frequent until the point where the fan would never turn off no matter what I tried unless I shut off the power to the furnace altogether. This problem has now carried over to the winter even when I have the heat on and the set temperature is reached. In both the cooling and heating setting the heat pump shuts down as it should but it is not followed up with the furnace fan shutting off as it would in the past.
What is the likely problem and the cause?

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Stuck fan control relay seems to be your problem but before replacing remove the G wire from the low voltage terminal strip located in the electric furnace. This will eleminate the possibility that the thermostat or shorted thermostat wiring is causing the problem. If the furnace blower still runs after the G wire is removed then it has to be the fan/blower control relay. The sad part is that if this relay is located on the circuit board the complete circuit board will need to be replaced.

Always test parts to be sure they are defective before replacing. There are always many possibilitys to a furnace problem. The information contained here is just the most likely cause of failure.

Xb90s sequence of events

Xb90 sequence of events