Mitsubishi HVAC Error Codes: Complete Troubleshooting Guide
⚠️ SAFETY FIRST: If you smell gas, hear electrical arcing, see sparks, or notice refrigerant leaks, turn off your system immediately and call ABC Air at [phone number]. Some HVAC repairs involve high voltage electricity and pressurized refrigerant that can cause serious injury or death.
Quick Error Code Lookup
🔴 EMERGENCY – Call ABC Air Immediately
- Error 4102: Electrical phase missing – DANGER: High voltage issue
- Error 4116: RPM/Fan motor failure – System shutdown required
- Error 4230: Overheating detected – Fire risk
🟡 URGENT – Same Day Service Recommended
- Error 1102: Temperature sensor fault – No heating/cooling
- Error 1301: Low refrigerant pressure – System damage possible
- Error 1302: High pressure fault – Compressor at risk
🟢 MODERATE – Schedule Service Within 24-48 Hours
- Error 0403: Communication error – Reduced efficiency
- Error 2502: Drain pump issue – Water damage risk
- Error 2600: Water leakage detected – Property damage possible
- Error 6600-6603: Network addressing conflict – Controls not working
- Error 6607: Lossnay communication failure – Ventilation affected
ℹ️ MINOR – Can Usually Wait Until Regular Business Hours
- Error 0900: Test mode activated – Simple reset needed
Detailed Error Code Information
Error 1102: Faulty Temperature Output 🟡
What it means: Your system's temperature sensor isn't reading correctly, so it can't properly heat or cool your home.
Most likely causes:
- Dirty or blocked condenser coils (most common – 70% of cases)
- Compressor overheating due to lack of airflow
- Faulty temperature sensor
- Refrigerant flow issues
What you can try first (5 minutes):
- Check and clean your air filter – replace if dirty
- Clear any debris around outdoor unit
- Ensure all vents are open and unblocked
- Wait 30 minutes, then restart system
When to call ABC Air:
- No heating or cooling after basic checks
- System repeatedly shuts down
- Unusual noises from outdoor unit
Typical repair cost: $200-$450 Parts: Temperature sensor ($45-$85), Coil cleaning ($150-$200) Time to fix: 1-2 hours
Error 0403: Internal Communication Error 🟡
What it means: The main control board and internal components can't communicate properly.
Most likely causes:
- Loose or damaged wiring connections
- Burnt connections on control boards
- Power surge damage
- Moisture in electrical connections
What you can check (10 minutes):
- Turn system off at breaker for 5 minutes, then back on
- Check that thermostat display is working normally
- Look for any loose wires at thermostat (don't touch – just observe)
⚠️ STOP HERE – Call ABC Air if:
- You see any burned or blackened wires
- Smell electrical burning odors
- System won't respond after reset
Professional diagnosis needed: This requires electrical testing and board diagnostics
Typical repair cost: $250-$600 Parts: Control board ($150-$350), Wiring repair ($100-$250) Time to fix: 1-3 hours
Error 0900: Test Operator 🟢
What it means: Your system is stuck in test/service mode.
What you can try (2 minutes):
- Locate the main control panel (usually near outdoor unit)
- Look for dip switches labeled “SW" or “TEST"
- Ensure test switch is in “OFF" or “NORMAL" position
- Restart system at main breaker
If problem continues: The control board may need professional reset
Typical repair cost: $85-$150 (service call only) Time to fix: 15-30 minutes
Error 1301: Low Pressure 🟡
What it means: Refrigerant pressure is too low for proper operation.
Most likely causes:
- Refrigerant leak (60% of cases)
- Blocked refrigerant lines
- Faulty pressure sensor
- System undercharged during installation
⚠️ Do NOT attempt DIY repair: Refrigerant work requires EPA certification and specialized equipment
Signs to watch for:
- Ice buildup on indoor coils
- Reduced cooling capacity
- Higher electric bills
- Hissing sounds near refrigerant lines
Professional service required: Leak detection, pressure testing, refrigerant recharge
Typical repair cost: $300-$800 Small leak repair: $300-$500 Major leak/coil replacement: $600-$1,200 Time to fix: 2-4 hours
Error 1302: High Pressure 🟡
What it means: System pressure is dangerously high, triggering safety shutdown.
Most likely causes:
- Blocked condenser coils (most common)
- Restricted airflow around outdoor unit
- Faulty fan motor
- Overcharged refrigerant system
- Blocked refrigerant lines
What you can check safely (15 minutes):
- Clear all vegetation/debris within 3 feet of outdoor unit
- Hose down condenser coils (system OFF) to remove dirt
- Check that outdoor fan spins freely when system starts
- Ensure no furniture/items blocking indoor vents
Call ABC Air immediately if:
- Outdoor fan not running
- Excessive vibration or noise
- System repeatedly trips breaker
- Steam or unusual odors
Typical repair cost: $200-$650 Coil cleaning: $150-$250 Fan motor replacement: $350-$550 Time to fix: 1-3 hours
Error 2502: Drain Pump 🟢
What it means: Water isn't draining properly from your indoor unit.
Most likely causes:
- Clogged drain line (80% of cases)
- Full condensate pan
- Failed drain pump
- Blocked drain outlet
What you can try first (20 minutes):
- Turn system off
- Locate condensate drain pan (usually under indoor unit)
- If safe to access, empty any standing water with wet/dry vacuum
- Check outdoor drain line for clogs
- Pour 1 cup white vinegar down drain line monthly for maintenance
⚠️ Water damage warning: Don't delay if water is overflowing – this can damage floors, walls, and ceilings
Call ABC Air for:
- Pump replacement
- Professional drain cleaning
- Recurring water issues
Typical repair cost: $175-$350 Drain cleaning: $125-$200 Pump replacement: $250-$400 Time to fix: 1-2 hours
Error 2600: Water Leakage 🟢
What it means: The system detected water where it shouldn't be.
Most likely causes:
- Humidifier malfunction
- Cracked drain pan
- Loose plumbing connections
- Frozen coil melting (in heating mode)
Immediate steps (10 minutes):
- Turn system off to prevent further water damage
- Place towels/containers to catch dripping water
- Take photos for insurance if damage is extensive
- Check humidifier water level and connections if equipped
Schedule same-day service if:
- Water is actively leaking
- You can't locate source of water
- Humidifier isn't working properly
Typical repair cost: $150-$400 Humidifier repair: $175-$300 Drain pan replacement: $125-$250 Time to fix: 1-2 hours
Error 4102: “Open Phase" 🔴
What it means: One of the three electrical phases feeding your system is missing – this is a serious electrical problem.
⚠️ ELECTRICAL HAZARD – Do not attempt any repairs
Most likely causes:
- Blown fuse in electrical panel
- Loose electrical connections
- Utility power issue
- Failed electrical components
Immediate actions:
- Turn system OFF at main breaker
- Do not touch any electrical components
- Call ABC Air immediately for emergency service
- Check if neighbors have similar electrical issues (utility problem)
Professional service required: Licensed electrician and HVAC technician
Typical repair cost: $200-$600 Electrical repairs: $150-$400 Component replacement: $200-$500 Emergency service: Additional $100-$150 Time to fix: 1-4 hours
Error 4116: RPM Error 🔴
What it means: Fan motor speed is incorrect or motor has failed completely.
This is the most complex error with multiple possible causes:
High Temperature Issues:
- Check area around heat recovery ventilator (HRV/ERV) for blocked airflow
- Ensure unit isn't in direct sunlight or near heat sources
Model Switch Problems:
- Control board may have wrong settings for your specific model
- Requires professional reprogramming
Fan Connection Issues:
- Loose motor wiring
- Burnt motor connections
- Failed motor starting components
Fan Motor Failure:
- Motor bearings worn out
- Electrical windings burned out
- Capacitor failure
Voltage Problems:
- Low voltage supply to motor
- Control board voltage output failure
⚠️ SAFETY WARNING: Turn system off immediately – failed fan motors can overheat and create fire risk
Professional diagnosis essential: This requires electrical testing, motor testing, and control board analysis
Typical repair cost: $300-$900 Motor replacement: $350-$650 Control board: $250-$500 Capacitor: $125-$200Time to fix: 2-4 hours
Error 4225: Low Voltage 🟡
What it means: Electrical voltage to fan components is insufficient for proper operation.
Most likely causes:
- Utility voltage problems
- Loose electrical connections
- Failed control board
- Damaged wiring
Check first (5 minutes):
- See if lights dim when system starts
- Check if other appliances are working normally
- Note any flickering lights in house
Call ABC Air for:
- Electrical testing and diagnosis
- Control board evaluation
- Wiring inspection
May also need electrician: If whole-house voltage is low
Typical repair cost: $200-$500 Control board: $250-$400 Electrical repairs: $150-$350 Time to fix: 1-3 hours
Error 4230: Overheating 🔴
What it means: System components are running dangerously hot.
⚠️ FIRE RISK – Turn system off immediately
Most likely causes:
- Motor overheating due to overload
- Blocked airflow causing heat buildup
- Electrical problems creating excess heat
- Failed cooling components
Immediate actions:
- Turn system OFF at main breaker
- Do not restart until professionally inspected
- Clear area around unit of any combustible materials
- Call ABC Air for emergency service
Never ignore this error: Overheating can cause fires, permanent equipment damage, and safety hazards
Professional service required: System safety inspection and repair
Typical repair cost: $250-$700 Motor replacement: $350-$600 Electrical repairs: $200-$450 Time to fix: 2-4 hours
Error 6600: Address Overlapping 🟢
What it means: Multiple units or controls are trying to use the same network address.
Most likely causes:
- Two units programmed with same address
- Network wiring problems
- Control system configuration errors
- Failed communication board
What this affects:
- Remote controls may not work properly
- Zone controls confusion
- Scheduling problems
- Temperature control issues
Professional service needed: Network configuration requires specialized knowledge
Typical repair cost: $150-$350 Programming/setup: $100-$200 Communication board: $200-$400 Time to fix: 1-2 hours
Error 6607: NO ACK ERROR 🟢
What it means: The Heat Recovery Ventilator (HRV/ERV) isn't responding to commands.
Most likely causes:
- HRV/ERV power loss
- Communication cable problems
- Address configuration changed
- Communication cable too long (over 500 meter limit)
- Failed HRV control board
What you can check:
- Verify HRV unit has power (lights/display on)
- Check that HRV is running when system calls for ventilation
- Look for any obvious damage to communication wires
Professional service needed: Network diagnostics and HRV repair
Typical repair cost: $200-$600 Communication board: $250-$450 Cable replacement: $150-$300 Time to fix: 1-3 hours
Symptoms-Based Troubleshooting
“My system isn't heating or cooling"
Most likely error codes: 1102, 1301, 4116, 4225 First steps: Check filter, verify thermostat settings, ensure power is onCall ABC Air if: No change after basic checks
“I hear unusual noises"
Most likely error codes: 4116, 1302, 4230 Types of noises:
- Grinding/screeching: Motor problems (4116)
- Hissing: High pressure (1302)
- Clicking/arcing: Electrical issues (4230)
“Water is leaking inside"
Most likely error codes: 2502, 2600 Immediate action: Turn off system, place containers to catch water Urgency: Same-day service to prevent property damage
“System keeps turning on and off"
Most likely error codes: 1102, 1301, 1302, 4230 Could indicate: Safety shutdowns due to overheating, pressure problems, or sensor issues
“Remote control/thermostat not working"
Most likely error codes: 0403, 6600, 6607 Try first: Replace batteries, check for loose connections Professional help: Network and communication problems
Maintenance Tips to Prevent Error Codes
Monthly Tasks (15 minutes)
- Change/clean air filters
- Check condensate drains for clogs
- Clear debris from outdoor unit
- Test thermostat operation
Quarterly Tasks (30 minutes)
- Inspect electrical connections (visual only)
- Check refrigerant lines for damage
- Clean condenser coils if accessible
- Verify all vents open and unblocked
Annual Professional Maintenance
- Complete system inspection
- Electrical testing and tightening
- Refrigerant level check
- Motor lubrication and testing
- Control calibration
- Safety system testing
ABC Air Maintenance Plans: Ask about our preventive maintenance agreements that can help avoid 80% of these error codes through regular professional service.
When to Call ABC Air vs. DIY
✅ Safe DIY Tasks
- Changing air filters
- Clearing debris from outdoor unit
- Basic thermostat operation
- Resetting breakers
- Clearing condensate drains (if accessible)
⚠️ Call ABC Air
- Any electrical work
- Refrigerant-related issues
- Motor replacement
- Control board problems
- Network/communication issues
- Recurring problems
- Multiple error codes
🚨 Emergency Service Needed
- Electrical sparks or burning smells
- Refrigerant leaks
- System overheating
- Water damage in progress
- Complete system failure in extreme weather
Cost-Saving Tips
- Regular filter changes prevent 60% of error codes
- Annual maintenance reduces emergency calls by 75%
- Early diagnosis prevents minor issues from becoming major repairs
- Seasonal tune-ups extend equipment life by 5-10 years
- Prompt attention to error codes prevents cascading damage
Contact ABC Air
24/7 Emergency Service: 0434506979 Regular Service: 0434506979 Email: [email protected] Service Area: Sydney
Our technicians carry common parts for same-day repairs on most Mitsubishi error codes. Licensed, insured, and factory-trained for your safety and satisfaction.
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