Armstrong Heat Pump Error Codes and Troubleshooting Guide

The following guide explains common Armstrong heat pump error codes, probable causes, and practical troubleshooting steps to help homeowners and technicians diagnose issues efficiently. Clear descriptions, safety notes, and recommended fixes are included to support safe, effective repairs.

Code	Meaning	Common Causes	First Steps
EF	Evaporator Freeze Fault	Low airflow, dirty coil, refrigerant imbalance	Check airflow, defrost cycle, clean coil
HP	High Pressure	Blocked condenser, fan failure, overcharge	Inspect condenser, check fan, call pro
LP	Low Pressure	Refrigerant leak, compressor issue	Look for oil stains, contact HVAC tech
CF	Compressor Fault	Start relay, overload, motor failure	Perform electrical checks, verify power
PF	Power Failure / Loss	Supply interruption, control board fault	Reset, inspect breakers, test voltage

How Armstrong Heat Pump Error Codes Work

Armstrong heat pumps use a control board that monitors sensors and system parameters, then displays short alphanumeric codes to indicate faults. Codes are designed for quick identification of refrigeration, electrical, or airflow problems and can vary slightly by model and control version.

When a code appears, the controller often locks out compressor operation to prevent damage. Some faults auto-clear after conditions normalize, while persistent codes require manual intervention or professional service.

Locating The Error Code On Armstrong Units

Error codes appear on the indoor unit display, thermostat, or outdoor unit console depending on the model. Consult the unit label or manual for the exact display location and any sequence required to view detailed diagnostics.

If the code does not show but a fault is suspected, many Armstrong systems offer a diagnostic mode accessible via a button sequence on the control board or thermostat. Document the code and operating conditions—outdoor temperature, time since startup, and whether the unit was defrosting.

Common Armstrong Heat Pump Error Codes And Meanings

EF — Evaporator Freeze Fault

The EF code indicates the evaporator coil temperature dropped below safe limits, often due to inadequate airflow or refrigerant issues. Typical symptoms include reduced heating capacity and visible frost on the indoor coil.

• Causes: Dirty filters, closed vents, fan failure, low refrigerant, stuck metering device.
• Immediate Actions: Turn the system off, allow defrost, check filters and airflow, inspect coil for frost.
• When To Call A Pro: Repeated EF codes, evidence of refrigerant leak, or if airflow is normal but freezing persists.

HP — High Pressure

The HP code signals high discharge pressure in the refrigerant circuit. This protects the compressor from overheating and potential damage. Symptoms include frequent short cycling and possibly loud discharge noise.

• Causes: Blocked condenser fins, failing outdoor fan motor, high ambient temperatures, liquid line restriction, overcharge.
• Immediate Actions: Inspect the outdoor coil for debris, ensure the fan runs, clear obstructions around the unit.
• Professional Service: Pressure checks, valve inspection, and potential refrigerant recovery/recharge should be performed by certified technicians.

LP — Low Pressure

LP indicates abnormally low suction pressure, generally from refrigerant loss or metering device failure. Performance drops markedly and the unit may struggle to maintain set temperatures.

• Causes: Refrigerant leak, restriction, failed compressor suction components.
• Immediate Actions: Look for oil stains on fittings/lines, listen for hissing sounds, and stop the unit to prevent compressor damage.
• Professional Service: Leak detection, evacuation, and correct refrigerant charging by an HVAC professional are required.

CF — Compressor Fault

CF flags problems with the compressor or its start components. The compressor may not run, run intermittently, or trip on overload.

• Causes: Failed start relay/capacitor, motor winding issues, locked rotor, or electrical supply problems.
• Immediate Actions: Verify power at the unit, check fuses and breakers, and note any unusual smells or burn marks.
• Professional Work: Electrical testing, megger insulation checks, and compressor replacement when necessary.

PF — Power Failure Or Supply Fault

PF indicates power interruptions, unsafe voltage conditions, or control board faults. Symptoms include loss of display, unit resets, or erratic control behavior.

• Causes: Tripped breaker, loose connections, lightning surge, failed transformer, or control board error.
• Immediate Actions: Check household breakers, ensure outdoor power switch is on, and reset the unit following manufacturer instructions.
• Professional Service: Persistent PF codes or evidence of electrical damage warrant licensed electrician or HVAC technician intervention.

Troubleshooting Workflow For Homeowners

Follow a safe, structured process to diagnose many common Armstrong heat pump codes before calling a technician. Always disconnect power at the service switch or breaker before performing inspections that involve internal components.

1. Document the displayed code, ambient conditions, and recent system behavior.
2. Perform basic checks: thermostat settings, breakers, outdoor power switch, and visible wiring.
3. Inspect airflow: replace filters, ensure vents are open, and clear obstructions near the outdoor unit.
4. Examine coils and fans: remove debris, straighten fins, and verify fan operation.
5. If the issue persists or involves refrigerant/electrical components, contact a licensed HVAC technician.

Safety Precautions And When To Stop

Armstrong error codes can indicate conditions dangerous to untrained personnel. Stop work immediately and call a pro if there are signs of refrigerant leaks, burning smells, smoke, or if the compressor is hot to the touch.

Working on refrigerant circuits or high-voltage components requires EPA and electrical qualifications. Homeowners should limit DIY actions to non-electrical checks, filter changes, and clearing debris around the unit.

Preventive Maintenance To Reduce Fault Codes

Regular maintenance significantly lowers the chance of error codes and extends equipment life. Recommended tasks include scheduled professional tune-ups and homeowner checks.

• Quarterly/Seasonal: Replace or clean filters, clear vegetation around outdoor unit, inspect condensate drain.
• Annually: Professional inspection of refrigerant charge, electrical connections, blower motor, controls, and defrost cycle operation.
• Additional Steps: Install a smart thermostat for optimized operation and surge protection to safeguard the control board.

When To Call A Licensed HVAC Technician

Contact a certified technician when error codes persist after basic troubleshooting, or when issues involve refrigerant, compressor, or complex electrical systems. Technicians can perform pressure diagnostics, electrical tests, and component-level repairs.

Always provide the technician with the exact error code, observed symptoms, and any steps already taken to expedite diagnosis and reduce service time and cost.

Model-Specific Variations And Documentation

Armstrong product lines may use slightly different code sets or display formats. For precise diagnostics, reference the unit’s model-specific service manual or the serial plate on the equipment.

Manufacturers periodically update control software and code lists. Check Armstrong’s technical bulletins or contact their support for model-specific clarifications and firmware-related fixes.

Cost Expectations For Repairs

Costs vary by issue complexity and region. Simple filter/airflow fixes are low cost, typically under a few hundred dollars. Refrigerant repairs and leak fixes can range from several hundred to over a thousand dollars depending on parts and refrigerant type.

Major compressor replacement or control board swaps are among the most expensive repairs. Obtain multiple estimates and ensure technicians provide itemized quotes before work begins.

Additional Resources And Tools

Helpful resources include the official Armstrong product manuals, HVAC trade organizations, EPA refrigerant handling guidelines, and online technician forums. Useful tools include a multimeter, gauge manifold, refrigerant leak detector, and fin comb for basic maintenance and diagnosis by qualified users.

Keep a log of service events, error codes, and repairs. This history helps technicians identify recurring patterns and improves long-term maintenance planning for reliable operation.

Summary Of Key Takeaways

• Document Codes: Record error codes and operating conditions before making changes.
• Start With Airflow And Power: Many faults stem from simple airflow issues or electrical supply problems.
• Know Limits: Leave refrigerant and electrical repairs to licensed professionals.
• Prevent With Maintenance: Regular cleaning and annual professional service reduce error occurrence.

For model-specific code charts, consult the unit manual or contact Armstrong customer support. Providing accurate code information expedites diagnosis and helps ensure safe, cost-effective repairs.