My HVAC is a heat pump system, the air handler inside is a Goodman aspf183016ea. The whole system/house is about 3 years old, and is all electric. I recently moved into the home and noticed that the air handler blower would continue to run even when the set temp was reached, whether heating or cooling; the condenser unit outside would shut off correctly, but the fan would continue to blow. This even occurs when the thermostat is set to off (fan is set to auto). The fan would occasionally shut off, but it was very rare. I had a technician take a look and he said the issue was probably a bad relay switch. He replaced it, but I noticed the issue was still present and called him back. He said he wasn’t sure why it would still be doing this, but replaced it again with a “heavy duty” one and just ensured me that even if the fan blows, it wouldn’t draw much power.
Now, the fan does shut off when the set temp is reached, but it keeps turning on and off in 10-15 minute increments; I’ve timed it, and it’s not exact every time. I’ve also noticed when the fan does come on (when the set temp has been reached and shouldn’t be on), I hear an audible noise from the blower unit, like a switch activating, before the fan turns on. I’ve since replaced the thermostat (formerly a Honeywell FocusPro 6000) with a Nest Learning Thermostat E. All the connections were made accurately, and the heating/cooling/fan controls work properly, however the fan still switches itself on and off in the same intermittent manner. I know the Nest thermostat has a setting to run the fan every hour for a set amount of time but I haven’t activated this.
Is the problem still with the relay switch, and should I have a technician take a look again? What else could the problem be?