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Navien Tankless — Complete Diagnostic

All Models · Error Codes · Wiring · Testing · Parts

📞 Support
⚠️Safety First: Shut off gas supply and power before any repair. If you smell gas, evacuate immediately and call your gas utility. Gas-line repairs require a licensed technician.
Select Your Model
Choose a series to filter error codes, parts, and wiring diagrams
Condensing — NPE-2 Series (Current)
Condensing — NPE Series (Previous Gen)
Non-Condensing — NHW-A Series (Current)
Non-Condensing — NPN Series (Current)
Legacy — NR / NP / CR Series
📞 NAVIEN TECHNICAL SUPPORT
1-800-519-8794  ·  Mon–Fri 5am–5pm PT
navieninc.com  ·  Have serial number ready (label inside front cover)
Error Code Lookup
Covers NPE-2, NPE, NHW-A, NPN, NR/NP/CR series
Wiring Diagrams by Series
Schematic layouts for all major Navien tankless series. Click a series to expand.
📋 Wiring Color Code Reference
Wire ColorFunctionNotes
● RedLine voltage 120VACHot leg from breaker
● Blue / WhiteNeutral 120VACReturn to breaker
● Green / BareGroundEarth ground
● OrangeSensor signal low voltage (5VDC)Thermistors, flow sensor
● VioletIgnition high voltageDo not probe directly
● Gray / BrownCommunication busPCB-to-PCB signals
● BlackGas valve coil / switch24VDC control
● Teal / CyanFan motor signal / PWMVariable frequency drive
🔬 Component Testing Procedures
Multimeter specs and step-by-step testing for all major components. Always disconnect power before probing unless noted.
🔩 Parts & Part Numbers
Navien OEM parts organized by series. Verify with Navien tech support (1-800-519-8794) for your unit's specific serial number and manufacture date.
🔍 Symptom-Based Troubleshooting
No error code? Select your symptom.
🔧 Maintenance Schedule
Preventative maintenance for all Navien tankless models