52 Moderate Hard — consider a tech

Rinnai Tankless Water Heater 52 — Modulating Solenoid Valve Signal Abnormal

Rinnai Tankless Water Heater · Error code 52

What 52 Means

Abnormal feedback from the modulating gas solenoid that controls burner output (high/low fire).

Symptoms

  • Code 52 during operation
  • Unstable temperature output
  • Hunting between high and low fire

Common Causes

1
Failed modulating solenoid

Coil out of spec.

2
Wiring fault

Open or shorted harness.

3
Bad PCB driver

Board not pulsing solenoid correctly.

How to Fix It

  1. Power down unit.
  2. Reseat modulating solenoid harness.
  3. Measure coil resistance against spec.
  4. Replace gas valve assembly if solenoid is bad.
  5. Replace PCB if wiring and valve test good.

More Rinnai Tankless Water Heater Codes

02 02 — Power Interruption / Memory Loss 03 03 — Loss of Communication / EZConnect Issue 10 10 — Air Supply or Exhaust Blockage 11 11 — No Ignition 12 12 — Flame Failure 14 14 — Thermal Fuse / Overheat Cutoff

All Rinnai codes → All tankless water heater codes →

Verified against manufacturer documentation: rinnai.us

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician.