Rheem Furnace 2 Flashes — What It Means
On most Rheem furnaces, 2 flashes indicate the pressure switch is stuck closed or closed at a time it should be open. The control board sees the pressure-switch circuit in the wrong state before the inducer sequence begins, treating it as a pressure-switch fault. Always confirm the exact code definition on your furnace’s door-data label or installation manual, because Rheem control families vary by model.
This fault tells you the pressure switch is not behaving as the sequence expects. The switch should open when there is no call for heat and close only after the inducer creates proper draft. When it stays closed or fails to open, the furnace locks out to prevent unsafe operation.
Common Causes
- Failed pressure switch The switch diaphragm or contacts fail internally, leaving the circuit closed even without draft.
- Blocked or damaged pressure-switch tubing Cracks, kinks, water, or blockage in the rubber tubing prevent the switch from sensing correct draft signals.
- Condensate drain or trap restriction On high-efficiency models, water backup in the drain or trap affects draft and holds the pressure switch in the wrong state.
- Vent or intake blockage Obstructions in the flue pipe or fresh-air intake alter draft pressure and prevent the switch from opening or closing properly.
- Inducer motor or port obstruction Weak inducer performance or a blocked inducer port disrupts the draft signal to the pressure switch.
- Wiring or connector fault Loose, corroded, or damaged terminals at the pressure switch or control board create a false closed-circuit reading.
Step-by-Step Fix
- Verify the exact code definition on the door-data label or installation manual for your specific Rheem model to confirm 2 flashes means pressure-switch fault.
- Check the pressure-switch tubing for cracks, kinks, water, blockage, or disconnection at both the switch nipple and the inducer tap.
- Inspect the inducer port and vent piping for obstructions, debris, or restrictions in the flue and fresh-air intake that would alter draft pressure.
- Clear the condensate drain and trap (on condensing furnaces) to make sure water backup is not affecting draft or switch operation.
- Test the pressure switch with the inducer off. With no call for heat, the switch contacts should be open. If they read closed on a meter, the switch has failed.
- Inspect wiring and connectors at the pressure switch and control board for looseness, corrosion, or damage that could create a false closed reading.
- Replace the pressure switch if it does not change state correctly during the draft sequence and all tubing, venting, and drain paths are clear.
Parts Often Needed
| Part | Notes |
|---|---|
| Pressure switch | Amazon | Match the pressure setpoint stamped on the original switch or listed in your furnace manual. |
| Pressure-switch tubing | Amazon | Use correct-diameter rubber or silicone tubing rated for furnace draft sensing. |
| Inducer motor assembly | Amazon | Required if draft is weak or the inducer does not spin properly during the call sequence. |
| Control board | Amazon | Order the board by your furnace model number if the circuit is falsely reported and all field components test good. |
When to Call a Pro
Call a licensed HVAC technician if you are not comfortable working with gas appliances, 120V wiring, or draft-proving circuits. A technician has the meters and manometers to measure switch behavior, draft pressure, and circuit continuity accurately. If you have replaced the pressure switch and tubing but the fault persists, the problem may involve the inducer, venting design, control board, or an intermittent wiring issue that requires diagnostic tools and experience to isolate safely.