Error code reference

Lennox Furnace Error Code DS1 Slow Flash / DS2 ON

Primary, secondary, backup secondary or rollout limit switch open; limits must close within 3 minutes or unit goes into 1 hour Watchguard.

SourceLennox G61MP Series - Service Manual: Gas Furnacep. 11

Diagnostic procedure

The full DS1 Slow Flash / DS2 ON procedure

Step 1 is visible so you can confirm you are on the right page. The remaining steps, the ones that tell you whether to actually replace a part, unlock with any pass.

MyPros+ · DiagnosticsStep 1 preview
1
First diagnostic step
Check continuity across limit switches; check for restrictions on blower inlet air (including filter) and outlet air.

SourceLennox G61MP Series - Service Manual: Gas Furnacep. 11

More steps, wiring diagram references, and verified part numbers
Includes expected resistance and voltage values, connector pinouts, and supersession notes for replacement parts.
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Where this code is documented

6 manuals in the MyPros+ library document this code for Lennox furnace.

Models covered by the manuals that document this code

More models are covered than are listed here.

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