The answer to 'furnace repair not heating' is that there are several common causes, including a malfunctioning thermostat, a clogged air filter, issues with the pilot light or ignition system, or problems with the furnace's internal components. Symptoms may include the furnace not turning on, not producing warm air, or cycling on and off frequently.
In many cases, simple DIY troubleshooting and maintenance can resolve the issue, such as replacing the air filter or resetting the thermostat. However, if the problem persists or you're not comfortable working on the furnace, it's best to call a professional HVAC technician to diagnose and repair the issue. Attempting complex repairs without the proper expertise can be dangerous and may lead to further damage to the furnace.