Troubleshooting Noritz Error Code 70: What It Means & How to Fix

Error 70 on a Noritz tankless water heater is a specific diagnostic code indicating a Circuit Board Error. This means the unit’s internal computer, or Printed Circuit Board (PCB), has detected a functional failure within its own hardware or software logic. Essentially, the “brain” of your water heater has encountered a fault that prevents it from safely managing the ignition, gas flow, or temperature regulation.

When this happens, you will likely experience an immediate loss of hot water, and the unit may become completely unresponsive to remote commands. While a circuit board failure sounds daunting, it is often caused by external factors like power surges or loose connections. Don’t worry—with a systematic approach, this is a fixable issue that doesn’t always require a brand-new heater.

Symptoms

The most obvious sign of Error 70 is the numerical code flashing on your Noritz digital remote controller or the internal LED display. However, physical symptoms often accompany this code:

• Total Lack of Hot Water: The unit will enter a lockout mode for safety, meaning the burner will not ignite even if there is water flow.
• Audible Clicking or Silence: You may hear the unit attempt to click (spark igniter) and then immediately throw the code, or the unit may remain completely silent when the tap is opened.
• Intermittent Operation: In the early stages of board failure, the heater might work for a few minutes, shut down unexpectedly, and then display the error.
• Faint Burning Smell: In cases of a short circuit, you might detect a slight “electrical” or ozone smell coming from the front cover of the unit.

The Complete Solution

Follow these steps in order. We will start with the easiest fixes before moving to component replacement.

Step 1: The Hard Power Reset
Before diving into the hardware, try a “hard reset” to clear the board’s temporary memory. Unplug the water heater from the electrical outlet (or turn off the dedicated breaker). Wait at least 60 full seconds to allow the capacitors on the board to discharge completely. Plug the unit back in and attempt to run hot water. If the error was caused by a minor software glitch or a one-time power flicker, this may resolve it immediately.

Step 2: Accessing the Control Center
SAFETY WARNING: Disconnect the power before removing the cover. Use your Phillips-head screwdriver to remove the four screws holding the front panel in place. Carefully pull the panel toward you. Locate the PCB, which is usually housed in a plastic or metal casing on the right side or bottom of the internal cabinet. Check for any visible signs of damage, such as black scorch marks, melted plastic, or white powdery corrosion.

Step 3: Seating the Wiring Harnesses
With the power still off, locate the various plastic wiring bundles (harnesses) plugged into the board. One by one, firmly press them into their sockets. Even if they look connected, they may have backed out slightly. A “click” indicates a secure seat. If you see any wires that look frayed or pinched, this could be the source of your Error 70.

Step 4: Voltage Testing with a Multimeter
Turn the power back on (be extremely careful not to touch any live exposed wires). Set your multimeter to AC Voltage. Test the incoming power at the board’s main terminal. It should read between 108V and 132V. If the voltage is significantly lower or higher, the board may be throwing Error 70 as a protective measure against poor house wiring. If the voltage is correct but the board still fails, the PCB itself is likely defective.

Step 5: Replacing the Circuit Board
If the reset and harness checks fail, the board must be replaced. Take a photo of the original board’s wiring so you know exactly where every color-coded wire goes. Unplug the harnesses, unscrew the mounting screws, and swap in the new board. Ensure the “DIP switches” on the new board are set to the exact same positions (UP/DOWN) as the old board, as these control the unit’s specific configuration (e.g., Gas Type, Venting Length).

• Repair Difficulty: Intermediate to Advanced (Involves electrical components)
• Estimated Time: 45 to 90 minutes
• Tools Needed: Phillips-head screwdriver (No. 2), Needle-nose pliers, Digital Multimeter, Flashlight
• Estimated Cost: $0 (Reset) to $450 (Board Replacement)

What Triggers this Code?

Understanding the “why” behind Error 70 is crucial for preventing a repeat failure. Here are the most common deep-rooted causes:

1. Voltage Spikes and Surges: Tankless water heaters are packed with sensitive microprocessors. A nearby lightning strike, a utility company power surge, or even “dirty power” from a home generator can overwhelm the board’s capacitors, leading to a permanent hardware fault.
2. Moisture and Corrosion: If the venting is improperly installed or if there is a tiny leak from the heat exchanger, moisture can drip onto the PCB. Even high humidity in a basement can cause micro-corrosion on the solder joints, disrupting the flow of data across the board.
3. Vibration-Induced Loosening: Over years of operation, the vibration from the combustion fan can cause the wiring harnesses that plug into the circuit board to wiggle loose. If the board loses “communication” with a sensor for even a millisecond, it may trigger an Error 70.
4. Component Aging: Like any computer, the capacitors on the Noritz PCB have a lifespan. Over 10-15 years, these components can “leak” or bulge, losing their ability to hold a steady charge, which results in internal logic errors.

How to Prevent Error 70

Once you have restored your hot water, take these steps to ensure the circuit board doesn’t fail again:

• Install a Dedicated Surge Protector: Do not just plug the heater into a standard wall outlet. Use a high-quality surge protector specifically rated for appliances. This is the single best defense against Error 70.
• Monitor for Leaks: During your annual flush/descale, look at the top of the unit for any signs of water tracking. Catching a leak before it drips onto the electronics will save the PCB.
• Maintain Proper Clearance: Ensure the area around the water heater is dry and well-ventilated. Excessive dust or lint can settle on the board and cause overheating of the microchips.

Frequently Asked Questions

Q: Can I “jump” the board to bypass Error 70?
A: Absolutely not. Error 70 is a safety lockout. Bypassing board logic could lead to uncontrolled gas flow or a fire hazard. The board must be functioning correctly for the unit to operate safely.

Q: Is Error 70 covered under warranty?
A: Noritz typically offers a 5-year warranty on parts. if your unit was installed within the last 5 years, contact Noritz support with your serial number; you may be eligible for a free replacement PCB.

Q: My board looks fine, but the error persists. Is it definitely the board?
A: While Error 70 is almost always the board, in rare cases, a shorted internal component (like the fan motor or gas valve) can “backfeed” an error to the board. If a new board doesn’t fix it, those peripherals are the next suspects.