The answer to 'my preventive maintenance keeps shutting off' is that there are several common causes, including a tripped circuit breaker, clogged air filters, or issues with the thermostat or control board. This can lead to symptoms like the system shutting off prematurely, short cycling, or not reaching the desired temperature.
For a DIY troubleshooting approach, first check the circuit breaker and reset it if tripped. Then inspect and replace the air filters if they are dirty. If those don't resolve the issue, the problem may be with the thermostat or a more complex component that requires a professional HVAC technician to diagnose and repair.