Lennox Furnace Error Code E 250

E 250 indicates the limit switch circuit is open, which means the furnace control board cannot confirm a closed safety circuit through the limit switch or switches. This is a protective fault that stops heating operation to prevent unsafe temperatures from building up in the system. The furnace will enter a 1-hour soft lockout if the limit does not close within 3 minutes, then attempt to resume normal operation on its own once the fault clears.

Yes, the E 250 fault is tied directly to the furnace's overheating protection system, so it should be taken seriously and diagnosed promptly. The limit switch circuit is designed to prevent dangerous heat buildup in the heat exchanger, which could otherwise lead to equipment damage or a cracked heat exchanger over time. Do not repeatedly reset or override the fault without identifying and correcting the root cause.

Repair costs vary depending on the cause. If the fix is as simple as replacing an air filter, costs are minimal, typically under $30. A blower motor replacement can range from $200 to $600 or more depending on the motor and labor rates in your area. Limit switch replacement generally falls in the $100 to $300 range including parts and labor, though costs can vary by region and technician.

Start by checking your air filter and replacing it if dirty, then confirm all supply and return vents throughout the home are open and unobstructed. Next, verify the furnace is operating at the correct firing rate and that there are no blockages inside the heater itself. If those checks do not resolve the fault, the blower motor performance and the limit switch itself should be tested by a qualified technician.

A manual reset may temporarily clear the fault, but E 250 will return if the underlying cause has not been corrected. The furnace is designed to enter a 1-hour soft lockout automatically and will attempt to restart on its own after that period. If the condition causing the limit switch to open is still present, the fault will trigger again during the next heating cycle.