Possible Cause for Heat Pump Error A004 means that the heating source defaults to elements due to compressor malfunction.
The following steps can help you check the issue.
Confirm fan is operational while the compressor is on. (In case the fan is not operational, check continuity from the middle (ground) terminal to either outside the terminal. If there is a 60V or higher reading, the fan should be running and will need to be replaced. If not, replace the control board (rare)).
Make sure the filter screen is clean.
Inspect compressor and surrounding components for any obvious signs of a refrigerant leak (oily residue) If the compressor is not operational or there are signs of leakage, the unit will need to be replaced as we do not service sealed system parts.
Contact your local Authorized Rheem Service provider to schedule service, repairs, replacements or installation of a Rheem Hybrid Heat Pump. Contact Amor Plumbing on the web, call or SMS chat us at 408-649-3129 (please be sure to include your model and serial number information).
To check warranty on your Rheem water heater, can contact the Rheem Hybrid Technical Services Department at 800-995-0982.