There are a few reasons why your ecobee furnace might be turning on and off.
1. The thermostat is not set correctly.
The most common reason for a furnace to turn on and off frequently is that the thermostat is not set correctly. If the thermostat is set too high, the furnace will turn on to heat the house, but then it will turn off quickly because the house has reached the desired temperature. The furnace will then turn on again a short time later, and the cycle will repeat.
2. The filter is dirty.
A dirty filter can restrict airflow, which can cause the furnace to overheat and turn off. The furnace will then turn back on when it has cooled down, but it will likely overheat and turn off again soon after.
3. The blower motor is not working properly.
If the blower motor is not working properly, it cannot circulate the air throughout the house as efficiently. This can cause the furnace to overheat and turn off. The furnace will then turn back on when it has cooled down, but it will likely overheat and turn off again soon after.
4. The furnace is too big for the house.
If the furnace is too big for the house, it will heat the house too quickly and then turn off. The furnace will then turn back on when the house has cooled down, but it will likely overheat and turn off again soon after.
5. There is a problem with the furnace itself.
If there is a problem with the furnace itself, it may turn on and off frequently. This could be due to a number of factors, such as a faulty thermostat, a broken igniter, or a clogged gas valve.
If your ecobee furnace is turning on and off frequently, it is important to have it inspected by a qualified technician. The technician can diagnose the problem and make the necessary repairs.