6 blinks Line and neutral reversed

What the control is telling you

The STATUS LED on the furnace control flashes 6 times: the control sees hot (L1) and neutral swapped on the 115 V supply. With reversed polarity the control may not be able to prove flame, so the furnace can light and drop out or lock out.

Applies to: Rheem RGRM upflow and RGTM downflow/horizontal two-stage condensing gas furnaces (90 Plus)

Likely causes

• L1 (hot) and neutral swapped at the furnace junction box or in the supply wiring
• Wrong polarity at a receptacle or plug-in cord feeding the furnace
• Poor or missing ground at the furnace or control

Test and repair steps

1. Warning: Turn off power at the disconnect before opening the junction box; line voltage is present inside.
2. At the furnace junction box confirm the black supply wire goes to L1 (hot) and the white to neutral, and that the ground wire is connected.
3. With power on, measure L1 to neutral should read about 115 V, neutral to ground close to 0 V, L1 to ground about 115 V. If neutral to ground reads line voltage, the wires are reversed.
4. If the furnace is fed from a receptacle, check the receptacle for reversed polarity and correct it.
5. Correct the wiring, restore power and confirm the STATUS LED returns to steady on and the burners stay lit through a full heat call.

Settings for these units

• Filter sizes · Rheem RGRM/RGTM 90 Plus