The answer to 'how to fix thermostat' is to first identify the issue with your thermostat. Common problems include a faulty wiring connection, a malfunctioning thermostat, or a problem with the HVAC system itself. Once you've identified the issue, you can take steps to troubleshoot and fix the problem.
If the issue is with the thermostat itself, you may be able to replace the batteries or recalibrate the settings. However, if the thermostat is no longer functioning properly, you'll likely need to replace it. This is a relatively straightforward DIY project, but it's important to follow the manufacturer's instructions carefully to ensure a proper installation.