Rheem R801SA furnace code 26: Line and neutral reversed
Professional repair
What does code 26 mean on a Rheem R801SA (801S downflow) furnace display? Code 26 means the control has detected reversed line and neutral polarity on the furnace's power supply. Correct polarity matters because it can affect flame sensing.
Before you touch anything: the six signs that mean stop troubleshooting and call a pro →
Polarity must be measured and corrected at the supply wiring by a qualified technician or electrician. This is line-voltage work with shock risk.
Possible causes
- Supply wiring connected with line and neutral swapped TECH
Parts for this code
No model-verified part number is listed here. Have the fault diagnosed and the correct part matched to your furnace before ordering.
Questions about this code
What does code 26 mean on a Rheem R801SA (801S downflow) furnace display?
Code 26 means the control has detected reversed line and neutral polarity on the furnace's power supply. Correct polarity matters because it can affect flame sensing.
How do I fix Rheem R801SA furnace code 26?
Have a qualified technician or electrician verify and correct the supply polarity, then confirm the code clears on the next heat call. Mention any recent electrical work. Do not open the junction box or swap conductors yourself.
How much does it cost to fix Rheem R801SA furnace code 26?
Cost reflects the visit and the time to measure and rewire the supply connection. A failed furnace component is not implied by this code alone.
Applies to
R801SA / 801S downflow single-stage 80% furnace with PSC motor
Different Rheem generations use different code maps. If your series isn't listed, don't assume this meaning — check your blower-door label.
Verified against Installation Instructions for Downflow Single Stage Gas Furnaces, p.34
Verified against Rheem 801S Series Installation Instructions — OEM143-14 mirror, p.34
Last verified 2026-10-07 · page updated 2026-10-07 · how we verify
Related Rheem furnace codes
These codes use the same rheem 801s downflow single-stage control (manual 92-24161-143-14) system.
| Pattern | Meaning |
|---|---|
| 22Two-digit display: 22 | Main limit or HALC open |
| 33Two-digit display: 33 | Rollout limit open |
| 20Two-digit display: 20 | Twinning fault |
| 55Two-digit display: 55 | Pressure switch closed |