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Error code reference

Lennox Furnace Error Code E301

LSOM

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What the E301 error code actually means

Your Lennox system detected that the air conditioner compressor ran for more than 18 hours straight without successfully cooling the home, and a pressure safety switch shut it down as a protective measure. This usually means the system is low on refrigerant, has a dirty outdoor unit, or has another issue preventing it from cooling efficiently. A qualified HVAC technician should inspect the system before you attempt to run it again.

Diagnostic procedure

The full E301 procedure

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1
Confirm the fault
Power cycle the unit: switch off the breaker for 60 seconds, then restore power. If the code returns, the fault is persistent and the procedure below isolates the cause.
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Most common causes of E301

Ranked by how often they cause this code
  1. 1Low refrigerant charge or refrigerant leak
  2. 2Dirty or blocked condenser coil
  3. 3Restricted or failed metering device
  4. 4Insufficient airflow across indoor evaporator coil
  5. 5Faulty high or low pressure switch

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Questions people ask about E301

What does E301 mean on a Lennox furnace?
E301 is an LSOM fault indicating that the outdoor unit compressor ran in air conditioning mode for more than 18 consecutive hours and triggered a system pressure safety trip. The LSOM monitors system operation and logs this code when the compressor cannot satisfy the cooling demand within a normal time frame. It points to an underlying refrigerant system issue such as a leak, low charge, blocked coil, or restricted metering device.
Is it safe to keep running my system with an E301 error?
Running the system while the E301 fault is active is not recommended. The compressor has already been under stress from an 18-hour run cycle, and continued operation without resolving the root cause risks serious compressor damage. Allowing the unit to sit off until a technician can evaluate it is the safer approach.
Will resetting the system clear the E301 code permanently?
Resetting the system may clear the E301 code temporarily, but the fault will return if the underlying cause is not corrected. Because the code requires the compressor to run for more than 18 hours before triggering, the damage to components can accumulate over time with repeated resets. A proper repair addressing the root cause is necessary for the fault to be permanently resolved.
Can I fix E301 on my Lennox system myself?
Some basic checks such as replacing a dirty air filter, clearing debris from the outdoor condenser coil, and ensuring all supply and return vents are open can be done without professional help. However, diagnosing refrigerant pressure issues, detecting leaks, and recharging refrigerant require EPA 608 certification and professional equipment. A licensed HVAC technician should be called if basic checks do not resolve the issue.
How much does it cost to repair an E301 fault on a Lennox system?
Repair costs vary widely depending on the root cause. Cleaning a condenser coil typically costs between $75 and $200 for a service visit. Refrigerant leak repairs and recharge can range from $200 to $1,500 or more depending on the severity and location of the leak. A metering device or pressure switch replacement generally falls in the $150 to $600 range including labor.

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