Expanded exact-code directory
Rheem and Ruud standard gas furnace error codes
Rheem and Ruud standard gas furnace indicators as Rheem Manufacturing lists them, each with its meaning and the first safe check.
- 1-blink-soft-lockoutSoft lockout of one hour. Rheem's FAQ says
- 2-blinks-pressure-switch-remains-openPressure switch failure, remaining open: the negative pressure
- 4-blinks-pressure-switch-remains-closedPressure switch failure, remaining closed. Rheem's FAQ says
Every code
Every Rheem and Ruud standard gas furnace code: what it means and what to do
- 1-blink-soft-lockout
- 2-blinks-pressure-switch-remains-open
- 4-blinks-pressure-switch-remains-closed
- 5-blinks-twinning-fault
Rheem and Ruud standard gas furnace code 1-blink-soft-lockout
Soft lockout of one hour. Rheem's FAQ says no flame sense was detected after four ignition trials, meaning four flame failures during one call for heat.
Turn the thermostat off for 5 to 10 seconds, or turn off the furnace's 115 volt power supply for the same time.
Rheem's reset for a soft lockout is to turn off the 115 volt power supply to the furnace or turn the thermostat off for 5 to 10 seconds. If it locks out again, Rheem's FAQ lists what stops flame sensing: improper phasing or polarity, a poor or missing equipment ground, incorrect manifold gas pressure and a dirty flame sense rod. On an upflow 90+ furnace with a blocked drain, the drain switch opens and de-energizes the gas valve, and four such openings in one heating call lock the furnace out on flame failure.
Rheem and Ruud standard gas furnace code 2-blinks-pressure-switch-remains-open
Pressure switch failure, remaining open: the negative pressure switch circuit is open. Rheem's tech tip words it as the pressure switch remaining open.
Look for anything blocking the vent outside the house, without opening the furnace.
Rheem's FAQ checks for a technician: with a magnehelic gauge, verify the negative pressure from the induced draft blower is at least 0.1 inch beyond the switch's closing setting, check for a blocked pressure switch tube port on the induced draft blower housing, and check for a blocked or restricted vent pipe. Rheem lists what can keep the switch open: the blower not running to speed, a blocked vent, a damaged heat exchanger, or a crack or hole in a heat exchanger tube.
Rheem and Ruud standard gas furnace code 4-blinks-pressure-switch-remains-closed
Pressure switch failure, remaining closed. Rheem's FAQ says the switch contacts remain closed during the off cycle, and the points may have welded together or become stuck.
Note that the furnace will not start its ignition sequence while this code shows.
Rheem's FAQ says the furnace will not go into the ignition sequence if the pressure switch does not open from the previous call for heat. Replacing a stuck or welded pressure switch is a technician repair.
Rheem and Ruud standard gas furnace code 5-blinks-twinning-fault
Twinning circuit failure, on boards with the twinning feature only. Rheem's tech tip adds that its National Service Department has found the 5 blink code can occur in some situations when an electronic thermostat is used.
Look at whether a thermostat wire is connected to the twin terminal of the integrated furnace control.
Rheem's FAQ steps: make sure no thermostat wire is connected to the twin terminal, check the control board switch setting is right for the application, and, if two furnaces are twinned, make sure the boards in both are the same or they will not operate together. A twinning fault can also come from the thermostat or faulty thermostat wiring: remove the thermostat wires from the control and put a jumper from R to W to see whether the code goes away.
Rheem Manufacturing — Gas Furnace Technical Frequently Asked Questions