Ruud Central System Air Conditioner "vent mr heater" Questions

How to bypass thermostat on a Mr.Heater construction forced air 125,000 to 170,000 btu propane heater unsafe to run unchecked replace the thermostat

...heater have failed (if fuses were installed from the factory.). Items 1 and 2 are indications of poor airflow through the unit for some reason (dirty filter, closed vents, dirty evaporator/buildup of ...