Ruud Error Code 51: Gas Valve Fault

Severity
Critical
Type
digital display
Estimated repair cost: $200 — $500 (parts + labor)
Warning: A 'Gas Valve Fault' indicates a potential problem with the gas supply or control, which could lead to a gas leak or explosion. Shut down the furnace immediately and call for professional service.

How to Fix Ruud Code 51

  1. Step 1: Shut off the gas supply to the furnace immediately at the gas shutoff valve, usually located near the furnace.
  2. Step 2: Turn off the furnace power at the breaker.
  3. Step 3: Evacuate the premises and call a qualified HVAC technician or your gas company from a safe location.

How to Reset Ruud Code 51

  1. Turn off the furnace power switch, usually located on or near the unit.
  2. Turn off the circuit breaker for the furnace. Wait 30 seconds.
  3. Restore power at the breaker and flip the furnace switch back on.
  4. Set the thermostat to call for heat. If the error code returns after 2-3 ignition attempts, the fault requires repair.

Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.

What Does Ruud Error Code 51 Mean?

The Ruud furnace error code 51, 'Gas Valve Fault,' means the furnace control board isn't seeing the expected signals from the gas valve. The gas valve is responsible for controlling the flow of natural gas to the burners for combustion. This error can occur before, during, or after a call for heat. The furnace will likely shut down and lock out as a safety measure. This is a critical fault because uncontrolled gas flow can create a dangerous situation. It's important to address this issue promptly to prevent potential hazards and restore heating.

Common Causes

  • Faulty gas valve solenoid(s)
  • Wiring issues between the control board and gas valve
  • Defective furnace control board
  • Low gas pressure
  • Flame sensor malfunction falsely indicating no flame

Diagnostic Steps

If... Check Expected
Furnace displays error code 51 Measure voltage to the gas valve during a call for heat 24VAC
Gas valve receives proper voltage Measure the resistance across the gas valve solenoid(s) Specific resistance range per the gas valve's specifications (check the valve or furnace service manual)
Gas valve solenoid resistance is within range Inspect wiring harness and connections between the control board and gas valve for damage or loose connections Wiring and connections are intact and secure
Wiring is good, voltage is present, and solenoid resistance is in range Check gas supply pressure to the unit with a manometer 7-10 inches of water column (in. w.c.)

Applicable Ruud Models

Replacement Parts

Part OEM Number Est. Cost Where to Buy
Gas Valve 7000DMV-D20 — Find Part
Furnace Control Board 47-24020-04 — Find Part
Flame Sensor SP14241 — Find Part

Related Codes on Same Models

Other codes that affect the same Ruud model families as 51.

Code Description Severity
11 No Ignition Critical
12 Flame Failure Critical
13 Improper Combustion Critical
14 Overheat / Thermal Fuse Critical
15 Inlet Temp Sensor Fault Warning
16 Outlet Temp Sensor Fault Warning
21 Air Supply / Operational Switch Warning
24 Flow Sensor Malfunction Warning
29 Condensate Neutralizer Issue Warning
31 Inlet Water Filter Warning