What It Means
Corrupt or invalid model data card detected in communicating control.
Rheem AC & Heat Pump
Rheem AC & Heat Pump Error Code d4
Troubleshooting guide for the Rheem AC & Heat Pump system fault d4.
Possible Causes
- Unprogrammed or blank memory card.
- Wrong memory card model installed.
- Corroded or unseated card contacts.
- Memory card damage.
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
Communicating control on the outdoor or indoor unit has a memory/model data card installed, but the data on it is invalid, unreadable, or does not match the equipment it's plugged into. This differs from d1 (no shared data available at all — card missing or link down) and from d3 (data is valid but the airflow CFM demanded exceeds what the indoor unit can deliver): d4 is specifically a corrupt or mismatched card rather than an absent or performance-limited one. The system will not run properly in communicating mode until valid data is present.
All Recorded Causes
A memory card left blank or improperly programmed at the factory or during a board swap, the wrong card model installed for this specific unit/tonnage, a card damaged or corroded at the contacts, a card not fully seated in its socket, or a card carried over from a different piece of equipment during a repair. Confirm the card matches the outdoor/indoor model and serial number before replacing the control board itself.
Verify Before Replacing Parts
- Confirm the exact Rheem model family and ac and heat pump context before acting on a generic code description.
- Confirm board LEDs, wiring polarity, and model compatibility before replacing control boards — this Rheem fault points at a memory card left blank or improperly programmed at the factory or during a board swap, t….
- Check for intermittent communication faults caused by connectors, moisture, or damaged harnesses, and rule out confirm the card matches the outdoor/indoor model and serial number before replacing the c….
- After the correction, run the system long enough to confirm the ac and heat pump fault does not return under normal load.
Not sure which system this Rheem code is on?
ACLogics has guided diagnostics for 57 Rheem fault codes and asks the right questions to narrow it down.
