Lennox Heat Pump: Use the defrost control TEST pins to clear lockouts or force defrost
Use the defrost control TEST pins to clear lockouts or force defrost on a Lennox heat pump: A jumper on the TEST pins (P1) clears short cycle and five-strike lockouts and forces the unit into and out of defrost; the 30 s defrost off-delay does not work while it is fitted.
Applies to: Lennox EL16KP1 (Elite) and ML14KP1 (Merit) R-454B heat pumps, sizes -018 to -060, demand defrost control A108 (CMC1)
How to fix use the defrost control test pins to clear lockouts or force defrost: step by step
- Place the jumper on the TEST pins of P1.
- Use it to clear the lockout or to cycle the unit in or out of defrost.
- After testing, move the jumper back across the desired defrost termination temperature pins (factory setting 50 F).
If the unit shows an error code, look it up: Lennox Heat Pump codes
Models
Lennox EL16KP1
EL16KP1-018EL16KP1-024EL16KP1-030EL16KP1-036EL16KP1-042EL16KP1-048EL16KP1-060
Lennox ML14KP1
ML14KP1-018ML14KP1-024ML14KP1-030ML14KP1-036ML14KP1-042ML14KP1-048ML14KP1-060
Source: Lennox EL16KP1 Unit Information 100195 / ML14KP1 Unit Information 100108, Defrost Control Connections, Test Pins (P1) Function, p.31. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.