Skip to main content
Error code reference
Lennox Heat Pump Error Code 10
Option 2 safety device switch opens.
SourceLennox HP21 Series - Full Service Manual (Heat Pump)p. 15
Diagnostic procedure
The full 10 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 Option 2 safety device and wiring.
SourceLennox HP21 Series - Full Service Manual (Heat Pump)p. 15
More steps, wiring diagram references, and verified part numbers
Includes expected resistance and voltage values, connector pinouts, and supersession notes for replacement parts.
Unlock 10 procedure $9.95
Or subscribe: $29/month for all codes plus Max diagnostics, with 70 Max messages a day. Plus applicable tax.
Where this code is documented
1 manual in the MyPros+ library documents this code for Lennox heat pump.
Models covered by the manuals that document this code
75,000+ service documents · 20,000+ error codes · 100+ brands
Get Started$29/month · Cancel anytime · Or $9.95 3-day pass · Plus applicable tax