Navien E432: cold water inlet 2 sensor fault

Navien heaters measure incoming water temperature to decide how hard to fire. Some models have two inlet sensors. E432 means the second one is giving an electrically invalid reading.

The meaning below comes from Navien's manuals for its NPE condensing tankless water heaters. Navien directs owners to its technical support line (1-800-519-8794) or a licensed installer for this code.

Common causes

• A loose, wet or corroded connector
• Damaged wiring between the sensor and the control board
• A failed sensor, sometimes after freezing

The repair

A technician inspects the connector and wiring and measures the sensor. If it reads open or shorted, it is replaced. It is a small, inexpensive part; the labor involves shutting off the water and opening the cabinet.

How to reset a Navien

1. Close all hot water taps.
2. Turn the unit off with the power button on the front panel, wait about a minute, then turn it back on.
3. Open a hot tap and watch whether the code returns.

Before you call

Have the model and serial number from the rating label ready, along with the exact code and when it appears: at startup, during use, or only at high demand. Mention any recent work on the gas, water or electrical supply and when the heater was last descaled. This helps the technician bring the right parts and often saves a second visit.

See every code on our Navien error codes page.