Rinnai · Tankless Water Heater Moderate

52 — Modulating Solenoid Valve Signal Abnormal

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

Keep using it?
Yes, with caution
DIY difficulty
Hard
Verified against
rinnai.us ↗

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.

Why it happens

Typical signs: Code 52 during operation · Unstable temperature output · Hunting between high and low fire

  • Failed modulating solenoid Coil out of spec.
  • Wiring fault Open or shorted harness.
  • Bad PCB driver Board not pulsing solenoid correctly.

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 →

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: rinnai.us.