Thermocouple
Common pilot and ignition part on gas water heaters.
Navien Error Code E013 — What It Means
Navien E013 indicates a domestic hot water (DHW) inlet temperature sensor fault — the cold water inlet thermistor is reading outside its valid range (open circuit, short circuit, or severely out-of-spec resistance). This sensor measures the temperature of the incoming cold water, which Navien uses to calculate how much heat to apply to reach the desired outlet temperature. Without a valid inlet reading, the unit cannot modulate accurately and shuts down to prevent scalding or damage.
Common Causes
- Failed DHW inlet thermistor — The sensor element fails (open or short), causing the board to read an invalid signal.
- Loose sensor connector — The thermistor connector at the PCB or at the sensor mounting location vibrates loose.
- Corroded or water-damaged connector — Moisture ingress corrodes the sensor connector pins, increasing resistance and producing an out-of-range reading.
- PCB thermistor input failure — Rarely, the board’s thermistor input circuit fails; sensor tests fine but the board still stores E013.
Step-by-Step Fix
- Locate the DHW inlet thermistor — Open the Navien service panel. The cold water inlet sensor is typically a small thermistor mounted in a well on the cold water inlet pipe, near the flow sensor assembly.
- Inspect the connector — Check the sensor connector at both the sensor and the PCB. Look for moisture, corrosion, or backed-out pins. Clean with electrical contact cleaner and reseat firmly.
- Measure thermistor resistance — With power off, disconnect the sensor. Measure resistance across the two sensor wires. At room temperature (~70°F/21°C), a Navien thermistor typically reads ~10 kΩ. Compare to the resistance-temperature table in your service manual. Out-of-range = replace.
- Check for shorts to ground — Measure from each wire to the unit chassis. Should read open (∞ Ω). Any finite reading indicates a shorted thermistor or wire.
- Replace the thermistor — The DHW inlet thermistor on most Navien NR/NPE series units is secured by a clip or a compression fitting. Match the part number to your model. Reinstall and tighten securely.
- Reset and verify — Power off for 30 seconds, restore, and draw hot water. Confirm E013 is cleared and the unit fires normally.
Parts Often Needed
| Part | Notes |
|---|---|
| DHW inlet thermistor | Navien model-specific — verify part number for NPE vs. NR series |
| Thermistor connector repair kit | If pins are corroded and sensor itself is good |
Need Replacement Parts?
Before ordering, match the water-heating part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
When to Call a Pro
If the sensor measures in-spec and connections are clean but E013 persists, the PCB has a failed input and requires replacement. Navien PCB replacement should be done by a Navien-trained technician to ensure the new board is matched and configured correctly for your unit’s model and gas type.