A3
Miller
High Limit or Auxiliary Limit Open
Miller furnace digital display shows A3; blower may run but no heat is produced.
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
Overheating due to restricted airflow, Failed blower motor or capacitor, Faulty limit switch, Loose wiring to limit circuit
How to Fix / Troubleshooting
Safety: Allow the furnace to cool and turn off power before accessing internal components.
- Check filter and airflow: Replace dirty filters and ensure all supply and return vents are open. Inspect ductwork for collapses or blockages.
- Inspect blower motor: Verify the blower starts promptly on a heat call. If it hums or fails to start, test and replace the run capacitor or blower motor as needed.
- Locate and test limits: Using a multimeter, check continuity across the main high limit and any auxiliary limits when the furnace is cool. Replace any open limits with Miller-approved parts.
- Secure wiring: Tighten any loose spade connectors in the limit circuit.
Advertisements
Repair Difficulty
Medium
3/5
Required Part
High Limit Switch
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements