Skip to main content
Error code reference
Lennox Air Conditioner Error Code E443
Incorrect appliance unit size code selected.
SourceLennox XC25 Series - Full Service Manual: Installation & Operationp. 35
Diagnostic procedure
The full E443 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 for proper configuring of unit size codes. If replacing inverter, verify inverter model matches unit size. Remove thermostat from the system while applying power and reprogramming.
SourceLennox Air Conditioner - Service Manual: Elite Series XC20p. 35
More steps, wiring diagram references, and verified part numbers
Includes expected resistance and voltage values, connector pinouts, and supersession notes for replacement parts.
Unlock E443 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
2 manuals in the MyPros+ library document this code for Lennox air conditioner.
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