Takagi Error Code 710: PCB Fault

Severity
Warning
Type
digital display
Estimated repair cost: $300 — $650 (parts + labor)
Warning: The Takagi water heater has detected a problem with its main control board (PCB) and has shut down. This requires troubleshooting to restore hot water.

How to Fix Takagi Code 710

  1. Step 1: Turn the unit OFF and then back ON using the power switch. This might reset a temporary error.
  2. Step 2: Check the main electrical panel for tripped breakers. Reset the breaker if necessary.
  3. Step 3: If the error persists after power cycling and checking the breaker, contact a qualified HVAC technician to diagnose and repair the unit.

How to Reset Takagi Code 710

  1. Turn off the unit using the power button on the front panel.
  2. Turn off the gas supply valve.
  3. Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
  4. Restore power at the breaker, then open the gas valve.
  5. Turn the unit back on. If the error returns, the underlying issue needs repair.

Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.

What Does Takagi Error Code 710 Mean?

The Takagi 710 error code indicates a fault within the Printed Circuit Board (PCB), which is the main control board of your tankless water heater. This board is essentially the 'brain' of the unit, responsible for managing all operations, from monitoring temperature sensors and flow rates to controlling the gas valve and ignition sequence. A fault here means the unit can't reliably control these functions, so it shuts down as a safety measure. The PCB monitors many internal sensors, and the 710 code is a general error that can be triggered by a variety of internal faults. Because the PCB manages so many functions, a 710 error can sometimes be triggered by other failing components.

Common Causes

  • Power surge or electrical noise damaging the PCB components.
  • Loose or corroded wiring connections to the PCB.
  • Internal component failure on the PCB itself (e.g., capacitor, resistor, or integrated circuit).
  • Software or firmware corruption on the PCB.
  • A connected sensor or component is sending invalid data to the PCB, causing it to fault.

Diagnostic Steps

If... Check Expected
Unit displays 710 error Check the voltage to the PCB 120VAC
Voltage is good Inspect wiring harness connectors to the PCB for corrosion or loose connections Connectors are clean and secure
Wiring is good Check resistance of thermistors connected to the PCB Resistance matches temperature chart
Thermistors are good Check the exhaust fan motor voltage DC voltage present when unit attempts to start

Applicable Takagi Models

Replacement Parts

Part OEM Number Est. Cost Where to Buy
Main PCB — — —
Wiring Harness — — —
Flame Rod — — —

Related Codes on Same Models

Other codes that affect the same Takagi model families as 710.

Code Description Severity
101 Combustion Abnormality Critical
111 Ignition Failure Critical
121 Flame Failure Critical
200 Overheating Warning
207 Bypass Valve Error Warning
291 Flow Rate Issue Warning
312 Outlet Temp Sensor Warning
321 Inlet Temp Sensor Warning
391 Exhaust Temp Sensor Warning
510 Gas Solenoid Valve Critical