Rheem Furnace 5 Blinks: Meaning and Fix
Applies to: Rheem standard single-stage gas furnace controls (Rheem's diagnostic code page excludes modulating, LXE and two-stage furnaces).
Also shown as: 5 blinks, five blinks, 5 flashes
Reading the furnace display
A furnace reports faults on a small status LED on the control board, seen through the sight glass in the blower door, or on a two-digit display. Watch a full cycle of the pattern and count the flashes, including the pause between groups, before you decide what you saw. The code chart is on the label inside the blower door.
This page lists the fault codes this brand documents, with likely causes and a short repair path. Check the model label on your unit before using any chart.
What causes 5 Blinks
- Twinning wiring fault between two furnace controls
- An electronic thermostat that triggers the code
- Control board fault
How to fix it
If you smell gas, leave the building and call your gas utility from outside; do not touch switches or the furnace. Switch the furnace power off before you open the blower door or touch the igniter or flame sensor, and call a licensed HVAC technician if you are not sure.
The code meaning comes from the manufacturer document listed under Sources. The causes and steps below are general troubleshooting guidance, not the manufacturer's service procedure.
- Switch the furnace power off before touching any wiring.
- If your furnace is not twinned, the code may be related to an electronic thermostat. A technician can confirm this.
- Check the thermostat wiring for loose connections, with power off.
- A technician should check the twinning wiring and the thermostat connection.
- Restore power and run a heating cycle. If the code returns, call a licensed HVAC technician and give them the code, the board label and the furnace model number.
Questions
What does 5 Blinks mean on a Rheem furnace?
On a standard Rheem gas furnace control with a twinning feature, 5 blinks mean a twinning circuit failure. Rheem's National Service Department notes the 5 blink code can also occur in some situations when an electronic thermostat is used.
Can I reset the furnace myself?
The control can be reset by switching power off at the furnace switch or breaker for about 30 seconds, which clears some lockouts. If the same code returns, the fault is still present and the control will shut the furnace down again. Never bypass a safety switch to keep it running.
When should I call a technician?
Call a licensed HVAC technician for anything involving gas, the pressure switch, the limit or rollout switches, the igniter, the flame sensor or a control board replacement, or if the code keeps coming back after the simple checks.
Other brands with code 5 Blinks
The same code can mean something different on another maker's appliance. Check the brand before you act.
Other Rheem furnace codes
Sources
Part numbers are OEM references; confirm fit by your model number before ordering. Meanings compiled from manufacturer and parts-retailer documentation; see sources below. Unplug the appliance before opening it.