Rheem R96VA0702317MSA Error Code 58: Water Circuit Open

What Does Code 58 Mean?

Because the Rheem R96V is a four-position condensing furnace, it wrings extra heat out of the flue gas and produces liquid condensate that collects in a collector box. Two water sensors sit in that box to catch a condensate backup, and both are wired back to connector P4 on the R96V Integrated Furnace Control (IFC). The IFC constantly looks for electrical continuity between pins 1 and 2 of P4 to confirm that both sensors are present and their wiring is intact.

Code 58 (Water Circuit Open) is posted when that continuity disappears. To the control this means a sensor has been unplugged or removed, the P4 connector is not fully seated, or the harness between the board and the collector box has been cut, chafed, or broken. It is not a report that water is present — it is the opposite: the sensing loop itself is missing, so the furnace can no longer trust its own leak detection.

Rheem treats this as a critical fault: the furnace will not run in gas-heat modes, though cooling and fan-only calls still work if the thermostat asks for them. Do not confuse code 58 with code 59 (Water Sensed), which is the reverse condition — code 59 means the IFC detected current flow indicating actual water in the collector box, while code 58 means the sensing loop is open. This is board-level wiring work inside a live gas appliance and is not a homeowner repair.

What You'll Notice

• The furnace will not fire for heat, but the air conditioner and the fan-only setting still run normally
• The dual 7-segment display on the R96V control shows 58
• The code frequently appears right after furnace service, a filter-cabinet swap, or condensate-pan work where a connector may have been left loose
• There is no water visible in or under the furnace, unlike a true condensate backup
• The house is not reaching the thermostat setpoint because gas heat is locked out

Common Causes

How This Is Diagnosed

A technician isolates code 58 by working the sensing loop from the board outward. They first confirm the P4 connector is fully seated on the IFC and that pins 1 and 2 are clean and not backed out of the housing, then trace the harness to the collector box looking for cut, pinched, or melted insulation. With power off they check continuity between pins 1 and 2 through both water sensors; an open reading points to a broken wire, a corroded terminal, or a sensor that was removed and never reinstalled.

This description is informational. Verifying continuity, reseating board connectors, and repairing or replacing the sensor harness are diagnostic steps for a qualified HVAC technician, not a DIY task, because the work is inside the control cabinet of a live gas appliance.

When to Call a Professional

This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:

• Code 58 appears and the furnace will only run cooling or fan, never heat
• The code showed up immediately after someone serviced the furnace or worked near the condensate collector box
• The 7-segment display keeps returning to 58 after power has been cycled
• A water sensor or a loose connector is visible near the collector box but you are not sure how it should be wired
• You also see code 59 at other times, suggesting the whole water-detection circuit needs inspection

✓ Verified against manufacturer service manual — March 2026