Rheem R802VA07542117MSA Error Code A223_F: Internal Fault: Monitor Chip Comm Failure

What Does Code A223_F Mean?

The Bluetooth Communicating IFC (Integrated Furnace Control) in your two-stage, variable-speed R802VA07542117MSA is not a single processor. It uses a main control processor that runs the heating sequence plus a separate safety monitor chip whose only job is to independently double-check that the main processor is behaving safely, especially around the gas valve and flame circuits. The two are supposed to stay in constant communication so each can verify the other. Code A223_F is logged when the main processor tries to reach that monitor chip and gets no valid response.

Because the monitor chip is the board's built-in second opinion on safety-critical decisions, Rheem's control will not keep running normal heat cycles while the two halves cannot agree. Losing that internal cross-check is treated as a hard failure of the board rather than a warning, so the furnace shuts down instead of continuing on the main processor alone. Nothing outside the board, no flame sensor, pressure switch, or gas valve, is being blamed by this code; the fault is entirely inside the printed circuit board's own electronics.

This makes A223_F a member of the internal-fault family on this board, alongside the flame-status-circuit failure A224_F and the general internal-fault lockout A093_F. A093_F is the catch-all "something internal went wrong" hard lockout, while A223_F is more specific: it names the processor-to-monitor communication link as the thing that failed. It is unrelated to the configuration and model-data codes A221_F and A222_F, which are about corrupt stored data that can sometimes be reprogrammed; a broken internal communication link between chips cannot be reprogrammed away.

Manufacturer guidance for this kind of internal monitor-communication failure is control board replacement. Power surges are the most common outside contributor, but even then the damage is to the board's own circuitry, so the remedy is the same.

What You'll Notice

• The furnace will not start a heat cycle and no warm air is delivered
• The alphanumeric LED blinks "A223_F" one digit at a time with a roughly three-second pause between digits
• The furnace stays locked out and does not respond normally to the thermostat
• The fault returns immediately even after power is cycled at the breaker
• The Bluetooth contractor app reports an internal control fault rather than any sensor-specific problem

Common Causes

How This Is Diagnosed

A technician first confirms the board is receiving correct, stable line and 24-volt power and checks for evidence of a recent surge or moisture damage, since a bad supply can make a healthy board report internal faults. With power confirmed good, they connect through the Bluetooth contractor app to read the exact fault and rule out the configuration and model-data codes (A221_F/A222_F) that can look similar from the outside.

Because A223_F points at the internal link between the main processor and the safety monitor chip, there is no external part to swap and no meter test on a wire that will clear it. If the fault persists with confirmed-good power and it is not a stored-data problem that can be reprogrammed, the diagnosis lands on the control board itself, and the technician's conclusion is board replacement.

When to Call a Professional

This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:

• The A223_F code returns immediately every time power is restored
• The furnace will not run any heat cycle at all
• The fault appeared right after a power outage, lightning storm, or nearby electrical surge
• The Bluetooth contractor app confirms an internal control or monitor-chip fault rather than a sensor code
• You smell gas at any point near the furnace or gas piping

✓ Verified against manufacturer service manual — March 2026