🚿Water Heater

E04

A.O. Smith · HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater

A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater E04 Error Fix: Compressor Discharge Over-Temperature

The compressor discharge temperature has exceeded safe operating limits. The heat pump compressor is overheating. This can be caused by inadequate airflow around the unit, dirty air filter/evaporator coils, refrigerant charge issues, or high ambient temperatures. Clean the air filter and evaporator coils. Ensure minimum 750 cubic feet of air space around the unit. Verify the room temperature is within the operating range (37°F to 120°F). If the problem persists, the refrigerant charge may need professional service.

High severity2 fixes available✨ Free fix available

Quick Answer

Error E04 on the A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater means: Compressor Discharge Over-Temperature. The top-ranked community fix is “Check Refrigerant Charge and Inspect Evaporator Coils” (hard difficulty, ~90 min, DIY cost: $0-$20). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · water heater

Content is based on manufacturer service documentation, community repair experience, and OEM technical bulletins. Always verify with your owner's manual.Learn about our editorial standards.

When to Call a Professional

While many water heater repairs can be done safely at home, consider hiring a qualified technician if:

This is a high severity error — continued use may cause damage or a safety hazard
The repair involves electrical wiring, gas lines, or refrigerant
You've tried the top-ranked fix and the error persists
You smell gas, see sparking, or notice water leaking
The repair requires specialized tools you don't have
Your appliance is still under manufacturer warranty

Average professional repair cost for this issue: $250-$450.

Other A.O. Smith Models with Error E04

AHPTU-80 Voltex Hybrid 80 Gal 4500W Hybrid Heat Pump Water Heater with WiFi Connectivity

water_heater · 2 fixes

Other A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater Error Codes

E01

Upper Tank Sensor Failure

2 fixes

E02

Lower Tank Sensor Failure

Dry Fire / ECO Trip

Evaporator Coil Sensor Failure

2 fixes

E06

Condenser Fan Motor Failure

Compressor Failure

High Pressure Switch Activated

2 fixes

E09

Low Ambient Temperature

2 fixes

People Also Ask About A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater Error E04

What does error code E04 mean on a A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater?

Error code E04 on the A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater means: Compressor Discharge Over-Temperature. The compressor discharge temperature has exceeded safe operating limits. The heat pump compressor is overheating. This can be caused by inadequate airflow around the unit, dirty air filter/evaporator coils, refrigerant charge issues, or high ambient temperatures. Clean the air filter and evaporator coils. Ensure minimum 750 cubic feet of air space around the unit. Verify the room temperature is within the operating range (37°F to 120°F). If the problem persists, the refrigerant charge may need professional service.

How do I fix error code E04 on my A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater?

The most successful fix is "Check Refrigerant Charge and Inspect Evaporator Coils" (hard difficulty, ~90 minutes). Estimated DIY cost: $0-$20. HomeMD has 2 community-ranked fixes for this error.

Is error code E04 on a A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater serious?

This error is rated high severity. You should address it promptly — continued use could cause damage or safety concerns.

Can I fix A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater error E04 myself?

Yes — the top-ranked community fix ("Check Refrigerant Charge and Inspect Evaporator Coils") is rated hard difficulty and takes about 90 minutes. Tools needed: Multimeter, T20 Torx screwdriver, Coil brush, HVAC gauge set.

How much does it cost to repair A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater error E04?

DIY cost: $0-$20. Professional repair typically costs $250-$450. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater have?

The A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater has 8 other known error codes, including: E01 (Upper Tank Sensor Failure), E02 (Lower Tank Sensor Failure), E03 (Dry Fire / ECO Trip), E05 (Evaporator Coil Sensor Failure), E06 (Condenser Fan Motor Failure), and 3 more.

Which other A.O. Smith models have the E04 error?

Error code E04 also appears on 1 other A.O. Smith model: AHPTU-80 Voltex Hybrid 80 Gal 4500W Hybrid Heat Pump Water Heater with WiFi Connectivity. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater have?

The A.O. Smith HPTU-50N HE Hybrid 50 Gal 4500W High Efficiency Hybrid Heat Pump Water Heater has 8 other known error codes:

E01 — Upper Tank Sensor Failure (2 fixes)
E02 — Lower Tank Sensor Failure (2 fixes)
E03 — Dry Fire / ECO Trip (2 fixes)
E05 — Evaporator Coil Sensor Failure (2 fixes)
E06 — Condenser Fan Motor Failure (2 fixes)
E07 — Compressor Failure (2 fixes)
E08 — High Pressure Switch Activated (2 fixes)
E09 — Low Ambient Temperature (2 fixes)

Which other A.O. Smith models have the E04 error?

Error code E04 also appears on 1 other A.O. Smith model:

AHPTU-80 Voltex Hybrid 80 Gal 4500W Hybrid Heat Pump Water Heater with WiFi Connectivity (water heater) · 2 fixes

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