Rheem Furnace Code 58: Water Sensor Circuit Open (Meaning, Causes, Fixes)

What the code means

Rheem's installation manuals name code 58 slightly differently by furnace line: "Water Sense Circuit Open" on R92P/R95P-type furnaces, "Water Circuit Open" on R96V and 802V furnaces, "Drain Circuit Open" on R96P/R96T, and "Water Sensor Jumper Not Attached" on the ultra-low-NOx 801T. They all describe the same thing: the integrated furnace control (IFC) checks for electrical continuity through the water sensor circuit, and code 58 means that continuity is missing. On the R96V, the manual says the control looks for continuity between pins 1 and 2 of connector P4 to confirm that both water sensors are present and connected. On the 80% 802V, which has no condensate sensors, the same pins are simply connected by a jumper wire. Rheem calls 58 a critical fault: no gas heating will run while it's displayed, but other modes such as cooling should work normally if there's a call for them. Code 59 is different: it means the sensors detected water, usually from a blocked condensate drain.

Likely causes

• A water sensor connector that's loose, unplugged or not fully seated at the sensor or at the control board's P4 plug (Rheem R96V manual)
• Damaged wiring between the control board and a water sensor, such as a pinched, chafed or broken wire (Rheem R96V manual)
• A water sensor that was removed and not reinstalled, for example during drain or collector box service (Rheem R96V manual)
• On 80% furnaces without condensate sensors, a missing or damaged jumper wire or connector at P4 (Rheem 802V manual)
• A failed water level sensor or, less often, a faulty control board after the wiring and connections check out

Safe DIY checks

1. Write down the code and whether it alternates with any other code. 58 alone points to the sensor circuit, while 59 means water was actually detected.
2. Think about recent work. If the furnace, condensate trap, drain or collector box was just serviced or the furnace was just installed, a sensor plug may not have been reconnected.
3. Turn off power to the furnace at its switch or breaker, then remove the access door. Look at the small water sensor wires near the collector box or condensate trap and at the plug where they meet the control board. Push any loose plugs firmly back together and look for wires that are pinched, cut or pulled loose.
4. Check that the condensate drain and trap aren't overflowing. Water around the sensors can damage them and their wiring, and a backed-up drain causes code 59 later even if 58 clears.
5. Put the door back on (the door switch keeps the furnace off with it removed), restore power and call for heat. If 58 comes right back, call an HVAC technician.
6. Don't jumper or bypass the water sensor circuit on a condensing furnace. The sensors shut down heating when the drain backs up, protecting the furnace from water damage.

Parts that commonly fix it

Always match the part number to your exact model.

Related codes

• 0 Rheem Gas Furnace 0
• 11 Rheem Gas Furnace 11
• 30 Rheem Gas Furnace 30
• 57 Rheem Gas Furnace 57
• 68 Rheem Gas Furnace 68

All Rheem codes →

Sources

1. Rheem R96V installation instructions 92-24161-124-01, Table 18 fault codes: 58 Water Circuit Open (no continuity between P4 pins 1 and 2, water sensors (2) in the circuit, critical fault, gas heat stops but cooling works; causes and solutions), water sensor and condensate trap vent tube options
2. Rheem 802V downflow installation instructions 92-24161-149-06, Table 14 fault codes: 58 Water Circuit Open (P4 jumper wire on 80% models; repair or replace wiring or connector), model data card note
3. Rheem R95P installation instructions, Diagnostics and Fault Codes (58 Water Sense Circuit Open, 59 Water Sensed), via ManualsLib
4. Rheem R92PA troubleshooting chart ST-A1194-23 (fault code list: 58 Water Sensed Circuit Open, 59 Water Sensed)