304
Ariston
High Limit Thermostat Trip
Furnace displays error 304, high limit trips frequently during operation.
Advertisements
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Advertisements
Possible Causes
Insufficient airflow across heat exchanger, Dirty air filter (for warm-air models), Blocked supply or return ducts, Faulty circulation fan
How to Fix / Troubleshooting
Safety: Turn off power before opening blower compartments or ductwork.
- Check air filter: On Ariston warm-air furnaces, locate the return air filter. Remove and inspect; if dirty or clogged, replace with the correct size and rating.
- Inspect supply and return grilles: Ensure that furniture or rugs are not blocking vents. Open all registers fully.
- Check blower fan: Remove the blower access panel and inspect the fan wheel for dust buildup. Clean with a soft brush and vacuum while supporting the wheel.
- Verify blower operation: With power restored, set the thermostat fan to ON. If the blower does not run or is very weak, the motor or capacitor may be failing and should be replaced by a technician.
Advertisements
Repair Difficulty
Medium
3/5
Required Part
High Limit Thermostat
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements