Window AC Error Codes: LG, Frigidaire, GE & Friedrich
Modern window air conditioners display error codes on the LED panel when a fault is detected. These codes point to specific component failures — temperature sensors, communication faults, or protection lockouts — and can guide your diagnosis before deciding whether to repair or replace. This guide covers the most common codes across the four major window AC brands.
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Common Symptoms
- Error code on the display panel (E1, E2, P1, F1, etc.)
- Unit stops cooling and displays a code
- Unit runs briefly then shuts down with a code
- Display flashes alternating code and temperature readings
Most Likely Causes
- 1
LG Window AC Error Codes
LG: CH — communication error between control board and display. E1 — indoor room temperature sensor (thermistor) open or shorted. E2 — indoor evaporator coil sensor fault. E3 — fan motor lock or outdoor unit communication error. CH 05 / CH 10 — inverter communication or IPM fault on inverter models. Most E1 and E2 codes are thermistor failures ($10–$20 part).
- 2
Frigidaire Window AC Error Codes
Frigidaire: E1 — indoor ambient temperature sensor failure. E2 — indoor coil temperature sensor failure. E3 — outdoor coil temperature sensor failure. E4 — compressor protection / overcurrent lockout. E5 — voltage protection fault (supply voltage out of range). E8 — indoor fan fault. Most E1–E3 codes are thermistor failures. E4 codes require checking the refrigerant charge and compressor.
- 3
GE Window AC Error Codes
GE: E1 — room temperature sensor (NTC thermistor) failure. E2 — evaporator coil sensor failure. E5 — compressor overcurrent / protection mode. F1 — humidity sensor fault. P1 — voltage protection: unit has shut down due to supply voltage being too high or too low. P1 codes are common during utility voltage fluctuations — the unit will restart when voltage normalizes.
- 4
Friedrich Window AC Error Codes
Friedrich: Lo — low-pressure protection, often indicating low refrigerant. Hi — high-pressure protection: blocked condenser airflow, dirty condenser coils, or outdoor temperature too high. E1 — ambient temperature sensor fault. E2 — coil temperature sensor fault. E9 — communication fault between control boards. Friedrich codes above require cleaning condenser coils before further diagnosis.
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Quick DIY Checks
Do not attempt to add refrigerant to a window AC yourself. Refrigerant handling requires EPA 608 certification. Low refrigerant indicates a leak that must be repaired first.
- 1Note the full code: write down exactly what the display shows — E1, E2, CH, P1, etc. — and which brand/model you have. The same code letter can mean different things on different brands.
- 2Power cycle the unit: unplug the AC from the wall, wait 60 seconds, then plug back in. Many transient faults (voltage spikes, sensor glitches) self-clear with a power cycle. If the code returns immediately, the fault is persistent.
- 3For E1 or E2 (sensor codes): locate the thermistor sensor — a small bead or cylindrical component attached to a thin wire, clipped to the evaporator coil or placed in the return air stream. Inspect for physical damage, corrosion, or disconnected connectors. Thermistors can be tested with a multimeter — a room-temperature NTC thermistor typically reads 10kΩ at 77°F.
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Try Pro — $7.99/mo- 4For P1 (voltage fault) on GE/Frigidaire: check the outlet voltage with a voltmeter or by plugging in a different high-power device. Window ACs require 115V–125V (standard) or 208V–240V (large units). Voltages outside this range trigger protection shutdown. If your home voltage is consistently low, a plug-in voltage stabilizer can help.
- 5For Hi/Lo pressure codes on Friedrich or compressor protection on Frigidaire (E4): clean the condenser coil on the back of the unit and ensure there is at least 12 inches of clear space around the unit's exhaust area. If the pressure fault returns after cleaning and adequate clearance, the refrigerant charge is likely low — call an HVAC technician.
- 6Check the filter: a severely clogged filter can cause coil temperature sensor faults (the coil gets too cold from restricted airflow and ice formation triggers sensor readings outside normal range). Clean the filter and let the coil thaw before resetting.
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Repair vs Replace
Thermistor failures are inexpensive to repair ($15–$30 for the part). Communication board failures and compressor protection faults that persist after cleaning and power cycling usually indicate more serious issues — at that point, the age and cost of a window AC unit makes replacement more economical. Units under 5 years old with sensor faults are worth repairing; units 10+ years old with compressor codes are typically replaced.
Est. Repair Cost
$10–$30 (thermistor sensor); $0 (power cycle for transient faults); refrigerant service $150–$300+
Est. Replacement Cost
$150–$600 for a new window AC
Recommended Tools & Parts
- Buy on Amazon →
NTC Thermistor Sensor (Universal 10kΩ)
Universal 10kΩ NTC thermistor sensor for window AC temperature sensing. Fixes E1 and E2 codes on LG, Frigidaire, GE, and most other brands.
$8–$20
- Buy on Amazon →
Window AC Control Board
Replacement main control board for window AC units. Brand and model specific — search by your unit's model number from the label inside the front panel.
$30–$80
- Buy on Amazon →
Plug-In Voltage Protector
Surge and voltage protection device for window AC units — prevents P1 voltage fault codes caused by unstable utility voltage. Also protects compressor from voltage spikes.
$20–$50
Links are Amazon affiliate links (tag: fixitfastai-20). Prices are estimates.
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Frequently Asked Questions
- My LG window AC shows CH but no other code — what does that mean?
- CH alone (or CH followed by a number) on LG units indicates a communication error between the main control board and the display/user interface board. On simple single-board units, it typically means the control board has failed. On split-board units (where display board and main board are separate), inspect the ribbon cable or connector between the two boards first — a loose connector often causes CH codes.
- Frigidaire E4 code: does that always mean refrigerant is low?
- Not always. E4 on Frigidaire (compressor protection) can also trigger from: blocked condenser fins causing high head pressure, a failed run capacitor causing the compressor to draw excess current, or a genuinely failing compressor. Clean the condenser coils and power cycle before assuming the refrigerant is low. If E4 returns immediately with clean coils and adequate airflow, call an HVAC technician to check pressure and the run capacitor.
- Is it worth paying an HVAC tech to service a window AC error code?
- For units under 5 years old with sensor codes — yes, the part cost is low and the repair is simple. For units 8+ years old with compressor or refrigerant codes — the service call and refrigerant cost ($150–$300) often approaches or exceeds the cost of a replacement unit. Get a quote, compare to replacement cost, and consider that a repaired older unit may develop additional problems soon after.