E7
Rheem
Indoor Unit Communication Loss
Thermostat displays E7 and may indicate 'Equipment communication error' or 'No response from indoor unit'.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Open or shorted communication wiring between thermostat and indoor unit, Indoor control board not powered, Blown low-voltage fuse on indoor board, Failed communication processor on indoor control board
How to Fix / Troubleshooting
Safety first: Turn off power to the indoor unit at the breaker before accessing the control compartment.
Steps:
- Verify indoor unit power: Confirm the air handler or furnace has line voltage and that its blower runs when called directly (if possible). Check any service switches.
- Check low-voltage fuse: Locate the 3–5A automotive-style fuse on the Rheem indoor control board. If blown, replace with the same rating after finding and correcting any shorts in the thermostat wiring.
- Inspect communication terminals: At the indoor board, verify the ABCD or designated communication terminals are wired correctly and firmly.
- Test with short cable: Temporarily connect the thermostat to the indoor unit with a short test cable. If E7 clears, the in-wall cable is damaged.
- If indoor board is unresponsive: Status LEDs on the board should be checked against the Rheem service manual. A non-blinking or error pattern may indicate a failed board that needs professional replacement.
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Repair Difficulty
Hard
4/5
Required Part
Indoor Unit Control Board
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