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Mitsubishi · MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit

Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit F4 Error Fix: Outdoor Heat Exchanger Thermistor Error

The outdoor coil temperature sensor (TE thermistor) has failed — open circuit, short circuit, or reading out of range. This sensor monitors the outdoor heat exchanger temperature for defrost control (heating mode) and high-pressure protection (cooling mode). Check the thermistor connector and wiring. Measure resistance — approximately 10K ohms at 25C. A failed outdoor coil thermistor will prevent proper defrost cycling in heating mode, leading to ice buildup on the outdoor unit.

critical2 fixes available✨ Free fix available

Quick Answer

Error F4 on the Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit means: Outdoor Heat Exchanger Thermistor Error. The top-ranked community fix is “Test and Replace Outdoor Heat Exchanger Thermistor” (medium difficulty, ~40 min, DIY cost: $10-$20). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · heat pump

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 heat pump repairs can be done safely at home, consider hiring a qualified technician if:

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: $100-$160.

Other Mitsubishi Models with Error F4

MXZ-3C30NAHZ 30,000 BTU 3-Zone Hyper-Heat Multi-Zone Outdoor Unit

mini_split · 2 fixes

MXZ-4C36NAHZ 36,000 BTU 4-Zone Hyper-Heat Multi-Zone Outdoor Unit

heat_pump · 2 fixes

PUZ-A18NKA 18,000 BTU P-Series Ducted Heat Pump Outdoor Unit

heat_pump · 2 fixes

PUZ-HA36NKA5 36,000 BTU Zuba Central Cold-Climate Heat Pump Outdoor Unit

heat_pump · 2 fixes

SUZ-KA09NA 9,000 BTU Concealed Duct System Outdoor Unit

heat_pump · 2 fixes

Other Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit Error Codes

Reverse Phase / Phase Loss Detection

2 fixes

Compressor Discharge Temperature Protection

2 fixes

Compressor Overheating / High Pressure Switch Activation

2 fixes

Outdoor Subcooling Sensor / Pipe Thermistor Error

2 fixes

High Head Pressure Protection

2 fixes

Compressor Overcurrent Protection (CT Sensor)

2 fixes

Heat Sink / Power Module Overheat Protection

2 fixes

High Pressure Switch (63H) Activated

2 fixes

People Also Ask About Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit Error F4

What does error code F4 mean on a Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit?

Error code F4 on the Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit means: Outdoor Heat Exchanger Thermistor Error. The outdoor coil temperature sensor (TE thermistor) has failed — open circuit, short circuit, or reading out of range. This sensor monitors the outdoor heat exchanger temperature for defrost control (heating mode) and high-pressure protection (cooling mode). Check the thermistor connector and wiring. Measure resistance — approximately 10K ohms at 25C. A failed outdoor coil thermistor will prevent proper defrost cycling in heating mode, leading to ice buildup on the outdoor unit.

How do I fix error code F4 on my Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit?

The most successful fix is "Test and Replace Outdoor Heat Exchanger Thermistor" (medium difficulty, ~40 minutes). Estimated DIY cost: $10-$20. HomeMD has 2 community-ranked fixes for this error.

Is error code F4 on a Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit serious?

This error is rated critical severity. It is generally not urgent and can often be resolved with a simple DIY fix.

Can I fix Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit error F4 myself?

Yes — the top-ranked community fix ("Test and Replace Outdoor Heat Exchanger Thermistor") is rated medium difficulty and takes about 40 minutes. Tools needed: T20 Torx screwdriver, Digital multimeter, Needle-nose pliers.

How much does it cost to repair Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit error F4?

DIY cost: $10-$20. Professional repair typically costs $100-$160. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit have?

The Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit has 8 other known error codes, including: F1 (Reverse Phase / Phase Loss Detection), F3 (Compressor Discharge Temperature Protection), F5 (Compressor Overheating / High Pressure Switch Activation), F6 (Outdoor Subcooling Sensor / Pipe Thermistor Error), F7 (High Head Pressure Protection), and 3 more.

Which other Mitsubishi models have the F4 error?

Error code F4 also appears on 5 other Mitsubishi models: MXZ-3C30NAHZ 30,000 BTU 3-Zone Hyper-Heat Multi-Zone Outdoor Unit, MXZ-4C36NAHZ 36,000 BTU 4-Zone Hyper-Heat Multi-Zone Outdoor Unit, PUZ-A18NKA 18,000 BTU P-Series Ducted Heat Pump Outdoor Unit, PUZ-HA36NKA5 36,000 BTU Zuba Central Cold-Climate Heat Pump Outdoor Unit, SUZ-KA09NA 9,000 BTU Concealed Duct System Outdoor Unit. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit have?

The Mitsubishi MUZ-GL09NA 9,000 BTU Single-Zone Outdoor Unit has 8 other known error codes:

F1 — Reverse Phase / Phase Loss Detection (2 fixes)
F3 — Compressor Discharge Temperature Protection (2 fixes)
F5 — Compressor Overheating / High Pressure Switch Activation (2 fixes)
F6 — Outdoor Subcooling Sensor / Pipe Thermistor Error (2 fixes)
F7 — High Head Pressure Protection (2 fixes)
F8 — Compressor Overcurrent Protection (CT Sensor) (2 fixes)
F9 — Heat Sink / Power Module Overheat Protection (2 fixes)
FA — High Pressure Switch (63H) Activated (2 fixes)

Which other Mitsubishi models have the F4 error?

Error code F4 also appears on 5 other Mitsubishi models:

MXZ-3C30NAHZ 30,000 BTU 3-Zone Hyper-Heat Multi-Zone Outdoor Unit (mini split) · 2 fixes
MXZ-4C36NAHZ 36,000 BTU 4-Zone Hyper-Heat Multi-Zone Outdoor Unit (heat pump) · 2 fixes
PUZ-A18NKA 18,000 BTU P-Series Ducted Heat Pump Outdoor Unit (heat pump) · 2 fixes
PUZ-HA36NKA5 36,000 BTU Zuba Central Cold-Climate Heat Pump Outdoor Unit (heat pump) · 2 fixes
SUZ-KA09NA 9,000 BTU Concealed Duct System Outdoor Unit (heat pump) · 2 fixes

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