250
Easy Fix
Lennox · HVAC Systems (AC, Furnaces & Heat Pumps)
Dirty Filter Detection
Quick Answer
Error code 250 on your Lennox HVAC Systems (AC, Furnaces & Heat Pumps) means: Dirty Filter Detection. This is usually fixable — see the step-by-step guide below.
Likely Causes
How to Fix It
1
Remove and inspect the air filter, replacing if dirty
2
Verify the correct filter size is installed per the furnace specifications
3
Check that the filter is seated properly in its track or housing with no air gaps
4
If the code persists with a new filter, check for return duct restrictions or collapses
Pro Tip
This is a common issue that most users can resolve without specialized tools. Try the first step before moving on to more complex solutions.
Parts You May Need
Air filter (correct size per specifications)
Filter rack or housing (if damaged)
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