What It Means
Model plug missing, running on stored PCM memory value.
Carrier Heat Pump
Carrier Heat Pump Error Code 25-22
Troubleshooting guide for the Carrier Heat Pump system fault 25-22.
Possible Causes
- Unseated or missing model plug on PCM board.
- Incorrect model plug part number.
- Damaged plug pins or connector harness.
Not sure which one it is — or if it's none of these? Try ACLogics today.
Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
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Full Diagnosis
Model Plug Missing. The control does not currently detect a model plug installed on the PCM, or none was present when power was first applied, but a valid model configuration value is already stored in memory from a previous successful read, so the equipment can continue operating on that stored value. This is the soft version of the fault; code 25-62 is the hard-lockout counterpart, raised when no model plug is present and there is also no valid value in memory, which prevents the equipment from operating at all rather than running on a fallback. Even though the unit may run normally under 25-22, the missing plug should still be treated as an active problem, since a future power cycle or memory event with no plug installed could escalate it to a 25-62 no-operation lockout. The fault clears once a correct, properly seated model plug is installed and read successfully by the PCM.
All Recorded Causes
Install the correct model plug for this unit on the PCM as soon as possible, even though the equipment may currently be running from stored memory. Verify the model plug part number matches the unit's model number exactly — an incorrect plug can cause operating parameter mismatches even if it satisfies the presence check. Inspect the plug's connector and pins for damage or a poor seat, since a partially seated plug can read as missing. Do not leave the unit running on stored memory long-term — confirm the fix by cycling power after installing the plug and verifying the fault clears rather than reappearing. Address this before it escalates to code 25-62, which will stop the equipment from operating entirely.
Verify Before Replacing Parts
- Confirm the exact Carrier model family and heat pumps context before acting on a generic code description.
- Verify current draw, overload status, and control signal before condemning the compressor or drive, given that install the correct model plug for this unit on the PCM as soon as possible, even though t….
- Look for upstream conditions such as airflow or charge issues that may be pushing the compressor into protection, and check verify the model plug part number matches the unit's model number exactly — an incorrect p….
- After the correction, run the system long enough to confirm the heat pumps fault does not return under normal load.
Still unsure about this fault?
ACLogics walks you through Carrier Heat Pump diagnostics step-by-step — so you confirm the cause before swapping parts.
