Ruud U96VA0702317MSA Error Code 58: Water Circuit Open
What Does Code 58 Mean?
Code 58 on the Ruud U96VA0702317MSA means the Integrated Furnace Control cannot detect continuity between pins 1 and 2 of connector P4. As a condensing furnace, this model has two water sensors that watch for condensate backing up; the control looks for continuity across P4 to confirm both sensors are present and wired. When that continuity is missing, it declares the water circuit open.
This is a critical fault, so gas heat is blocked while cooling and fan still work. It is the open-circuit counterpart to code 59 (water actually sensed): code 58 says the sensing circuit itself is broken, whereas code 59 says the sensors detected water.
The most common cause is damaged wiring between the control and the sensors, or a loose connection at P4. A water sensor removed during previous service also breaks the circuit. Repairing wiring and connectors inside the furnace and replacing sensors is technician work.
What You'll Notice
- The furnace will not produce gas heat and shows code 58
- Cooling and fan continue to operate
- The fault can appear after service work that disturbed the water-sensor wiring or a sensor was left out
- The code persists until the P4 circuit continuity is restored
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Damaged wiring or loose connection at water sensor | Most common | ✗ Call a pro → |
| Water sensor removed | Common | ✗ Call a pro → |
How This Is Diagnosed
A technician inspects the wiring between the control and the two water sensors for damage and confirms the connection at P4 (and at the sensors) is fully seated, since a broken wire or loose connector is the most common cause of a lost water circuit.
They also confirm both sensors are actually present — one may have been removed during earlier service — and repair or replace wiring, connectors, or sensors as needed to restore continuity.
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:
- The furnace shows code 58 and will not provide heat
- The fault appeared after work near the water sensors or condensate area
- You suspect a water sensor is missing or its wiring is damaged
Frequently Asked Questions
What is the difference between code 58 and code 59?
Code 58 means the water-sensing circuit is open — a wiring or connection problem — while code 59 means the sensors actually detected water in the furnace.
Can I reconnect the water sensor wiring myself?
It involves internal control-board connectors and sensor wiring, so it should be handled by a technician who can safely restore continuity at connector P4 and verify the sensors.
✓ Verified against manufacturer service manual — March 2026