Two things make WS1 fault codes harder to look up than they should be.
The first is that the same fault displays differently depending on the board in front of you — E2, Err 102 and 1002 are one condition, not three. The second is less well known: the definitions changed between manual revisions, and a lot of what circulates online is still quoting the old ones. There are also codes in wide circulation that appear in no Clack manual at all.
This is the current table, taken from Clack's WS1 and WS1.25 service manual (Form V3115-99, revised January 2026), cross-checked against the WS1TT twin-tank manual and the current WS1.5P/WS2P manual. Where a code has an older or conflicting definition, it is flagged.
The current code table
| Letter | 3-digit | 4-digit | What the control is reporting |
|---|---|---|---|
| E1 | Err 101 | 1001 | Control unable to sense motor movement |
| E2 | Err 102 | 1002 | Motor ran too short and was unable to find the next cycle position |
| E3 | Err 103 | 1003 | Motor ran too long and was unable to find the next cycle position |
| none | Err 104 | 1004 | Motor ran too long and timed out trying to reach home position |
| none | Err 106 / 116 | 1006 | MAV / SEPS / NHBP / AUX MAV motor ran too long, unable to find proper park position |
| none | Err 107 / 117 | 1007 | MAV / SEPS / NHBP / AUX MAV motor ran too short (stalled) looking for park position |
That is the whole table. Six entries, and the letter forms stop at E3.
Three things this table settles
There is no E4 on a current WS1. Err 104 has no two-digit equivalent today. E4 appears in the 2008 service manual for the WS1.5, WS2 and WS2L valves — a different, now-superseded family — where it meant what Err 104 means now. If a reference hands you "E4" for a WS1, it is quoting an old document about a different valve.
Err 116 and 117 are not separate faults. The current manual lists 106/116 as one row and 107/117 as one row — alternate display strings for the same entry, same causes, same remedy. Some secondary references split them into distinct meanings; the manufacturer's documentation does not support that.
The 4xx codes are not in any Clack manual. A widely-circulated error-code PDF hosted by a parts retailer lists a 402–414 range covering EEPROM checksum, RAM and communication faults, and maps "E4" to code 403. None of it appears in the current WS1 manual, the WS1TT manual, the WS1TC OEM manual, the CI programming manual, or the current WS1.5P/WS2P manual. It may come from internal service documentation, but it cannot be verified against anything Clack publishes — treat a 4xx code, or an E4-means-403 claim, as unconfirmed.
The definitions that changed
Worth knowing if you are cross-referencing an older document or an article that quotes one:
| Code | Current WS1 manual (2026) | 2008 manual, WS1.5 / WS2 / WS2L |
|---|---|---|
| E1 | Control unable to sense motor movement | Unable to recognize start of regeneration |
| E2 | Motor ran too short and was unable to find the next cycle position | Unexpected stall |
They describe the same broken signal path from different angles, but the older phrasing is what most retailer troubleshooting posts still repeat. Check the revision date on whatever you are reading.
What to check first, whatever the code
Before you diagnose anything specific:
- Read the code off the display yourself. Not what the customer texted, not what a search result assumed. E2 and E3 are one character apart and point opposite directions.
- Confirm it is a Clack valve. Other manufacturers use the same letter codes for entirely unrelated faults — a search for a bare "E3" will return softener troubleshooting with a completely different fix path.
- Resynchronise. Hold NEXT and REGEN together for three seconds on standard boards, or SET and DOWN on TC boards — the physical button may be silkscreened SET HOUR, CLOCK or SET CLOCK. On either board, disconnecting power at the PC board for five seconds and reconnecting does the same thing. This drives the piston home and re-zeroes the position counter.
- If it returns immediately at the same point, you have confirmed a real fault rather than a one-off, and the code is now worth acting on.
Where each code sends you
E1, Err 101, 1001 — no motor movement sensed at all. Documented causes, in order: motor not fully inserted so its pinion doesn't engage, motor wires broken or disconnected; PC board not properly snapped into the drive bracket; missing reduction gears.
E2, Err 102, 1002 — stalled short. Causes: foreign material lodged in the valve; mechanical binding; main drive gear too tight; improper voltage to the PC board. This is the code that means resistance, and it usually means opening the valve.
E3, Err 103, 1003 — overran. Causes: motor failure during regeneration; foreign matter causing friction buildup; drive bracket not snapped in properly.
Err 104, 1004 — overran specifically while returning home. One documented cause: the drive bracket not snapped in properly. Worth knowing that home is found differently from every other position — by sensing the rise in motor current when the piston hits its mechanical stop, rather than by counting optical pulses.
Err 106 / 116, 1006 — the MAV or no-hard-water bypass motor overran looking for its park position. Causes: valve programmed for alternation with no MAV or NHBP actually attached; motor wire not connected to the board's DRIVE connector; motor not fully engaged with the reduction gears; foreign matter buildup. Note the first one — this is frequently a programming error, not a hardware fault.
Err 107 / 117, 1007 — the MAV or NHBP motor stalled looking for park. Causes: foreign material lodged in the valve; mechanical binding, including a jammed motor pinion.
How the valve knows where it is
Worth understanding once, because it explains why the codes split the way they do. The WS1 uses no cams and no limit switches. An optical sensor reads a reflective coating on one of three reduction gears, and the board counts reflected pulses as that gear turns — each cycle position has a defined count. Home is the exception: the board finds it by the rise in motor current when the piston reaches its mechanical stop, and the counter re-zeroes there.
So E2 and E3 are pulse-counting failures in opposite directions, and Err 104 is a current-sensing failure. Knowing which is which tells you whether to look at the piston or the gear train.
Key takeaways
- The current WS1 code table has six entries and the letter forms stop at E3 — there is no E4 on a current board.
- Every fault shows as a letter, a three-digit and a four-digit string depending on board generation; they are one condition.
- E1's and E2's definitions changed between manual revisions, and most sources online still quote the older wording.
- The 402–414 range and the "E4 = 403" mapping circulating online appear in no Clack manual — treat them as unverified.
- Resynchronise before diagnosing: NEXT and REGEN for three seconds, SET and DOWN on TC boards, or five seconds off at the PC board.
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Clack and Water Specialist are trademarks of Clack Corporation. Aquonyx is an independent manufacturer; this guide is not affiliated with or endorsed by Clack Corporation.