Lennox HVAC Error Code E12: How to Fix Compressor Inlet Over Current
Medium 30-60 minutes Medium Severity
Verified June 2026
- Error Code
- E12
- Brand
- Lennox
- Product Type
- hvac
- Severity
- Medium
- DIY Difficulty
- Medium
- Estimated Fix Time
- 30-60 minutes
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Tools You'll Need
- Multimeter with capacitance and ohms functions
- Insulated screwdriver (for capacitor discharge)
- Wire brush or contact cleaner
- Safety gloves and goggles
How to Fix Error Code E12
-
Power Off and Safety Check
High voltage inside the unit can cause serious injury or death. Always disconnect power and discharge capacitors before proceeding. -
Inspect the Run Capacitor
Capacitors can hold a charge even when power is off. Use an insulated screwdriver to short the terminals to discharge safely. -
Check Compressor Electrical Connections
-
Measure Compressor Winding Resistance
Ensure power is completely off before measuring resistance. -
Test for Ground Fault
-
Check Voltage at Contactors
Live voltage present. Be careful not to touch exposed wires. -
Assess Compressor Condition
Parts You May Need
Compressor run capacitor
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Compressor (if defective)
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Compressor run capacitor
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Compressor (if defective)
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Compressor run capacitor
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Compressor (if defective)
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Compressor run capacitor
Check Price on Amazon
Compressor (if defective)
Check Price on Amazon
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When to Call a Professional
If the compressor winding resistance is abnormal, you detect a ground fault, or the capacitor replacement does not clear the error, call a licensed HVAC technician. Replacing a compressor requires specialized tools and refrigerant handling, which must be done by a professional.Frequently Asked Questions
What does Lennox error code E12 mean?
Lennox error code E12 indicates a compressor inlet over current condition, meaning the compressor is drawing too much electrical current. This can be due to a bad capacitor, electrical issues, or a failing compressor.
Can I reset Lennox error code E12?
Yes, you can try resetting by turning off the HVAC system at the breaker for 5 minutes, then turning it back on. If the error returns, there is an underlying issue that needs to be fixed.
What causes compressor over current on a Lennox AC?
Common causes include a faulty run capacitor, low voltage supply, loose or corroded electrical connections, a mechanically stuck compressor, or an internal compressor short.
How much does it cost to fix Lennox error E12?
If the issue is a run capacitor, DIY cost is $10-$30. If a compressor replacement is needed, expect $1,500-$3,000 including labor and refrigerant. A service call to diagnose costs $100-$200.
Is it safe to run my AC with error code E12?
No, running the system with this error can damage the compressor further or cause electrical hazards. Turn off the system until the issue is resolved.