Error code reference
Lennox Heat Pump Error Code DS2:AlternatingFastFlash / DS1:AlternatingFastFlash
Coil sensor problem
Coil sensor problem — sensor detected open, shorted, or out of temperature range; board will not perform demand or time/temperature defrost.
First step from the service manual
Check coil sensor resistance at pins 5 & 6 (Brown wire); replace sensor harness if shorted or open.
The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.
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Get the full diagnostic procedure for DS2:AlternatingFastFlash / DS1:AlternatingFastFlash.
- Step-by-step tests with expected resistance, voltage, and continuity values
- Wiring diagram references and connector pinouts from the OEM service manual
- Verified part numbers when replacement is required
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