Ruud U802VA050317MSA Error Code A093_F: Internal Control Fault Detected

What Does Code A093_F Mean?

Code A093_F on the Ruud U802VA means the Bluetooth Communicating IFC has detected an internal control fault and placed the furnace in a hard lockout. A hard lockout differs from the timed one-hour and five-minute lockouts on this board: the furnace will not resume on its own, and power must be cycled only after the underlying fault has been repaired.

The important safety nuance is that A093_F is also set when the board detects voltage on the gas-valve contacts that it does not expect, and that voltage does not go away when the inducer is shut off. That specific signature indicates a welded gas-valve relay — the same failure the IFC reports directly as A225_F — where the relay contacts have fused closed and the control can no longer stop sending voltage to the gas valve. If that is the cause, gas could be commanded when it should not be, so it is treated as a potential gas hazard rather than a routine board error.

Because the board self-diagnostic cannot always specify whether A093_F is a general internal fault or the welded-relay condition, the safest reading is to assume the gas-valve side could be involved. Simply cycling power to clear the lockout does not fix the root cause and, if a relay is welded, would not remove the hazard. The IFC almost always requires professional evaluation and typically replacement, with power cycled only after the repair is complete.

What You'll Notice

• The contractor app or IFC shows A093_F and the furnace is in a hard lockout that does not clear on its own
• The furnace will not start a heat cycle and stays unresponsive to the thermostat
• Power cycling clears the display only briefly, and the fault returns without a repair
• In the welded-relay case, a gas odor near the furnace or burners that respond when they should be off
• The furnace does not behave normally after routine power interruptions

Common Causes

How This Is Diagnosed

A technician first determines whether A093_F is a general internal board fault or the welded gas-valve-relay signature, since the latter is a gas hazard. They check for unexpected voltage on the gas-valve contacts and observe whether it persists when the inducer is shut off — the pattern the board uses to flag a welded relay (the condition also reported as A225_F). They confirm the hard lockout will not clear by power cycling alone and evaluate the IFC's internal self-diagnostics. Because this involves the control board and the gas-valve circuit, the work is done by a qualified technician and is informational only — it is not a homeowner repair, and power should be cycled only after the board is repaired or replaced.

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:

• A093_F is present, since a hard lockout will not clear on its own and can indicate a welded gas-valve relay
• There is any smell of gas near the furnace, in which case leave immediately and call your gas company first
• The code returns after power is cycled, confirming the internal fault is still present
• The furnace also shows the A225_F welded-relay code or the burners respond when they should be off

✓ Verified against manufacturer service manual — March 2026