Direct answer: North Star NSC22 and NSC31 softeners show E1, E3, E4 or E5; the NSC42 shows the same faults as Err1, Err3, Err4 or Err5. Codes 1, 3 and 4 point to the valve drive: the wiring harness or connections to the position switch, the switch itself, a valve fault causing high motor torque, or a motor that does not run. Code 5 is an electronic control malfunction, corrected by replacing the control board. The NSC42 manual’s clearing procedure is to unplug the power supply, correct the problem, plug it back in and wait 8 minutes; the code returns if the fault is still there.
Publisher boundary: Water System Guide is an independent research publisher, not North Star support or a North Star dealer. This guide summarizes the troubleshooting sections of manual 7393624 (NSC22 and NSC31) and manual 7393632 (NSC42), both Rev. H dated January 7, 2026, reviewed October 15, 2026. NST two-tank models, the NSCWC and NSCWHC 2-in-1 systems and older controls are not covered. Motor, switch, harness and board work belongs with a North Star servicer.
The codes by model
The two manuals list the same causes and corrections, with different display formats (NSC22/NSC31 manual, PDF page 20; NSC42 manual, PDF page 20).
| NSC22 / NSC31 | NSC42 | Causes listed in the manual | Correction listed in the manual |
|---|---|---|---|
| E1, E3 or E4 | Err1, Err3 or Err4 | Fault in the wiring harness or connections to the position switch | Replace the wiring harness or connections to the position switch |
| Fault in the switch | Replace the switch | ||
| Fault in the valve causing high torque | Replace the rotor/seal | ||
| Motor inoperative | Replace the motor | ||
| E5 | Err5 | Electronic control malfunction | Replace the electronic control board |
The manuals group codes 1, 3 and 4 together. The number alone does not tell you which of the four causes applies, and there is no code 2 in either table. Record any code exactly as displayed, including whether it reads “E” or “Err.”
What the self-diagnostics do and do not watch
The NSC42 manual explains the scope: the softener “has a self-diagnostic function for the electrical system (except input power and/or water meter)” and “if a malfunction occurs, an error code appears in the display” (NSC42 manual, PDF page 21).
Two common failures therefore produce no code at all:
- No power. A tripped breaker or unplugged supply leaves the display blank. The troubleshooting table’s correction is to restore power, reset the controls and use Recharge Now.
- A stopped meter. If the turbine stops counting, the controller does not see water use, does not schedule recharges and lets the water turn hard, with a normal-looking display.
A third symptom sits next to the codes in the table: a motor that is “stalled or clicking.” The listed cause is a motor malfunction or an internal valve fault causing high torque on the motor, and the corrections are to replace the rotor and seal or the motor and switch. That is the mechanical condition behind many code 1, 3 and 4 events, so mention any clicking or grinding when you report a code.
For hard water without a code, use our North Star not-softening guide.
The low salt light is not an error either. The manuals say the light on the control panel is off in normal operation and flashes slowly with the salt level indicators when the salt monitor shows a low level and needs to be set (NSC31 manual, PDF page 12).
How to clear a code
The NSC42 manual lists four steps under “To remove an error code” (NSC42 manual, PDF page 21):
- Unplug the power supply from the electrical outlet.
- Correct the problem.
- Plug the power supply back in.
- Wait 8 minutes. The error code will return if the problem was not corrected.
The NSC22/NSC31 manual lists the same codes and corrections but does not print this procedure in the reviewed revision. Ask the servicer before assuming it applies identically.
Unplugging alone is a test, not a repair. While a code is displayed, the NSC42 manual says, “all buttons are inoperable except the SELECT button,” which stays active so the service person can run diagnostics.
The diagnostics screen
Both manuals describe the same manually initiated diagnostics (NSC31 manual, PDF page 21). Press and hold SELECT for three seconds. The display then shows:
- Turbine count. Three zeros with no water flowing. With soft water running, the count repeats from 000 to 199 for each gallon on the NSC22 and NSC31, and from 000 to 140 on the NSC42.
- Valve position indicator. Which cycle the valve is in.
- Position switch status. With the valve in service or any recharge position, the switch should show open; while the valve rotates between positions, it should show closed. “There is likely a problem if indications vary from this pattern.”
- Days powered. Press and hold UP.
- Regenerations counted. Press and hold DOWN to see how many regenerations the controller has started since the model code was entered.
The NSC42 diagnostics screen also shows the number of days since the last regeneration and the minutes remaining in the current cycle (NSC42 manual, PDF page 21). On both, the display returns to the time of day if no button is pressed for 4 minutes.
Checking the meter when the count stays at zero
If the turbine count stays at 000 with a soft-water faucet open, the manuals describe a quick sensor test. Pull the sensor housing from the valve outlet port and pass a small magnet back and forth in front of the sensor. “You should get a reading in the display. If you get a reading, unhook the inlet and outlet plumbing and check the turbine for binding.” No reading points toward the sensor, its wire harness or the board.
The model code check
Wrong configuration can look like a fault. When power is connected, the display briefly shows the model code: n22P for NSC22, n31P for NSC31 and n42P for NSC42 (NSC31 manual, PDF page 12; NSC42 manual, PDF page 12). The troubleshooting table lists “incorrect model code programmed” as a cause of intermittent hard water. If the code does not match the rating decal, the controller is running on the wrong capacity data; have the servicer correct it.
Parts named in the corrections
Every error correction is a part replacement. The valve parts lists give these order numbers (NSC31 manual, PDF page 27; NSC42 manual, PDF page 27):
| Part | NSC22 / NSC31 (3/4-inch valve) | NSC42 (1-inch valve) |
|---|---|---|
| Position switch | 7030713 | 7305150 |
| Motor, cam and gear kit | 7397864 | 7384691 |
| Rotor and disc | 7199232 | 7185500 |
| Seal kit | 7129716 | 7185487 |
| Sensor wire harness | 7309803 | 7309811 |
| Replacement electronic control board | 7360867 | 7369798 |
The electronic control board and valve body carry a five-year limited warranty in both manuals, longer than the one-year term on other parts. See our North Star parts guide for the full lists and how parts are ordered.
Factory reset is not on the error list
Both manuals describe “Resetting to factory defaults”: hold SELECT until the display changes twice to a flashing model code, press UP to show a flashing “SoS,” then press SELECT to restart. Time, hardness and all other settings return to defaults.
No error row lists a reset as the correction. A reset erases the settings a servicer needs to see and repairs nothing mechanical. If one is done, record every value first and re-enter them with our North Star settings guide.
Before calling the contractor
North Star softeners are sold and serviced through contractors, and the warranty directs owners to “contact your contractor” first. Have this ready:
- Model and serial number, the code exactly as shown, and whether it returned after 8 minutes.
- The model code (n22P, n31P or n42P) and the regeneration count from the diagnostics screen.
- Whether the turbine counts with a soft-water faucet open.
- When the code appeared and whether the softener was regenerating. Our North Star regeneration guide describes the normal cycle.
If the house needs water while you wait, move the bypass valve to bypass.
Frequently asked questions
What does E1 mean on a North Star water softener?
On the NSC22 and NSC31, E1 is grouped with E3 and E4: a wiring or connection fault to the position switch, a failed switch, a valve fault causing high torque, or a motor that does not run. The NSC42 shows the same faults as Err1, Err3 or Err4.
What does Err5 mean on a North Star NSC42?
Err5, shown as E5 on the NSC22 and NSC31, is an electronic control malfunction. The manual’s correction is to replace the electronic control board.
How do I reset an error code on a North Star softener?
The NSC42 manual says to unplug the power supply, correct the problem, plug it back in and wait 8 minutes. If the fault was not corrected, the code returns.
Is a flashing low salt light an error on a North Star softener?
No. The manuals say a slowly flashing low salt light with the salt level indicators means the salt monitor shows a low level and needs to be set after adding salt.