The answer to 'HVAC system not turning on' is that there are several common causes, including a tripped circuit breaker, a faulty thermostat, or issues with the HVAC unit itself. Symptoms may include the system not powering on at all or the fan not running. Solutions can range from simple DIY troubleshooting to more complex repairs that require a professional HVAC technician.
If the HVAC system is not turning on, the first step is to check the circuit breaker. If the breaker has tripped, simply reset it and see if the system powers on. If the breaker trips again, there may be an electrical issue that needs to be addressed by a professional. You can also check the thermostat to ensure it is set correctly and the batteries are working. If the thermostat appears to be functioning properly, the issue may be with the HVAC unit itself, such as a problem with the compressor, fan, or other internal components. In these cases, it's best to call in an HVAC technician to diagnose and repair the problem.