{"id":353992,"date":"2026-09-13T22:48:58","date_gmt":"2026-09-13T17:18:58","guid":{"rendered":"https:\/\/stitchpartner.com\/?p=353992"},"modified":"2026-09-13T22:49:03","modified_gmt":"2026-09-13T17:19:03","slug":"jack-c4-e4-overlock-error-codes-guide","status":"publish","type":"post","link":"https:\/\/stitchpartner.com\/hi\/jack-c4-e4-overlock-error-codes-guide\/","title":{"rendered":"JACK C4 \/ E4 Overlock Machine Error Codes: Complete Guide"},"content":{"rendered":"

Quick Answer<\/h2>\n

JACK’s E4 and E4S overlock machines run on the “C4” control box, and it shows its own error codes separate from JACK’s lockstitch machines. JACK’s official operation manual documents 11 codes \u2014 E1 through E7, plus EA, Eb, EC, and Ed. JACK’s own official maintenance videos also reference a newer, expanded numbered series (Error 01 through at least Error 26) used on updated C4 boards. This guide covers both, sourced directly from JACK’s official C4\/E4 operation manual and JACK Technology’s own “Quickservice” maintenance video series.<\/p>\n

What Is the JACK C4 Control Box?<\/h2>\n

C4 is the control box fitted to JACK’s E4 and E4S power-saving overlock (serger) machines \u2014 a different product line entirely from the F4\/F5\/F6 direct-drive lockstitch range and the A4\/K4 auto-trimmer range. Because it runs a four- or five-thread overlock stitch rather than a single-needle lockstitch, its control box watches a different set of motor and sensor conditions, which is why its error codes don’t match either of JACK’s other schemes.<\/p>\n

If your machine is a JACK E4 or E4S overlock and its panel shows a code, it almost certainly belongs to the list below rather than the F4\/F5\/F6 or A4\/K4 guides.<\/p>\n

JACK C4\/E4 Error Code Chart (Official Manual)<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Code<\/th>\nWhat It Means<\/th>\nQuick Fix<\/th>\n<\/tr>\n<\/thead>\n
E1<\/td>\nMotor stuck<\/td>\nReduce load, restart, check plug connection, check fabric weight and lubrication<\/td>\n<\/tr>\n
E2<\/td>\nMotor controller abnormal<\/td>\nWait a few minutes and restart; check that fabric isn’t too heavy<\/td>\n<\/tr>\n
E3<\/td>\nParameter save abnormal<\/td>\nRestart, or hold the reset button for 3 seconds; contact a dealer if unresolved<\/td>\n<\/tr>\n
\u09084<\/td>\nMotor Hall signal abnormal<\/td>\nInspect the 10-core connector and Hall sensor wiring<\/td>\n<\/tr>\n
E5<\/td>\nNeedle position signal abnormal<\/td>\nRotate the hand wheel, restart, check the positioner connection<\/td>\n<\/tr>\n
E6<\/td>\nSpeed governor abnormal<\/td>\nCheck the plug connection and coder wire; replace the governor if needed<\/td>\n<\/tr>\n
E7<\/td>\nCurrent detection circuit fault<\/td>\nClean the circuit board, check power voltage, restart<\/td>\n<\/tr>\n
EA<\/td>\nHardware over-current<\/td>\nDisconnect power, restart, check supply voltage, restore factory defaults<\/td>\n<\/tr>\n
Eb<\/td>\nSystem over-voltage<\/td>\nCut power immediately; adjust supply to the rated 220V<\/td>\n<\/tr>\n
EC<\/td>\nSystem under-voltage<\/td>\nCut power immediately; adjust supply to the rated 220V<\/td>\n<\/tr>\n
Ed<\/td>\nBrake resistor protection fault<\/td>\nCheck the resistor plug and voltage; restart or restore defaults<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Newer C4 Boards: The Extended Error 01\u201326 Series<\/h2>\n

JACK’s own official “Quickservice” maintenance video series (published by JACK Technology Co., Ltd) documents additional numbered fault codes on updated C4 control boards, beyond what’s in the original operation manual above. These appear on newer C4 boards as straight numbers rather than letter-plus-digit codes:<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Code<\/th>\nWhat It Means (per JACK’s official videos)<\/th>\n<\/tr>\n<\/thead>\n
Error 01<\/td>\nCovered in JACK’s official troubleshooting series<\/td>\n<\/tr>\n
Error 02<\/td>\nSoftware over-current<\/td>\n<\/tr>\n
Error 03<\/td>\nCommunication malfunction<\/td>\n<\/tr>\n
Error 07<\/td>\nSewing bed safety switch alarm<\/td>\n<\/tr>\n
Error 09<\/td>\nAbnormal pedal connection<\/td>\n<\/tr>\n
Error 10<\/td>\nCovered in JACK’s official troubleshooting series (October update)<\/td>\n<\/tr>\n
Error 11<\/td>\nOver-pressure (over-voltage) during shutdown<\/td>\n<\/tr>\n
Error 12<\/td>\nSystem under-voltage<\/td>\n<\/tr>\n
Error 13<\/td>\nAbnormal brake circuit<\/td>\n<\/tr>\n
Error 19<\/td>\nSystem detection circuit failure<\/td>\n<\/tr>\n
Error 26<\/td>\nCovered in JACK’s official troubleshooting series<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

If your C4 machine is showing a numbered code above that isn’t a simple restart-and-recheck fix, treat it the same way you would the equivalent lettered code \u2014 check plugs and connections first, then the power supply, and call a technician for anything that keeps recurring after that.<\/p>\n

JACK C4\/E4 Error Codes Explained One by One<\/h2>\n

E1 \u2014 Motor Stuck<\/h3>\n

E1 means the control box tried to drive the motor and met more resistance than expected. Turn the looper shaft or hand wheel by hand first to check for a mechanical jam \u2014 thread wrapped around a looper is the most common cause on an overlock machine. If it turns freely, reduce the load, check the motor plug, and restart.<\/p>\n

E2 \u2014 Motor Controller Abnormal<\/h3>\n

E2 shows up when the motor draws more current than expected for a sustained stretch, usually from fabric that’s too heavy for the setup or a machine overdue for lubrication. Power off, wait a few minutes, and restart. Check oil level and fabric weight if it recurs.<\/p>\n

E3 \u2014 Parameter Save Abnormal<\/h3>\n

E3 points to the control box failing to save its parameter settings correctly. Restart the machine, or hold the reset button for 3 seconds to force a reset. Contact your dealer if the fault doesn’t clear after a reset.<\/p>\n

E4 \u2014 Motor Hall Signal Abnormal<\/h3>\n

E4 means the motor’s Hall sensor signal has gone abnormal \u2014 inspect the 10-core connector cable and the Hall sensor wiring for looseness or damage before restarting. JACK’s own official maintenance video for the E4 machine covers exactly this fault.<\/p>\n

E5 \u2014 Needle Position Signal Abnormal<\/h3>\n

E5 points to the needle-position sensor rather than the main drive motor. Rotate the hand wheel by hand, restart the machine, and check that the positioner connector is fully seated. If your machine doesn’t need precise needle positioning, this function can be disabled by a technician.<\/p>\n

E6 \u2014 Speed Governor Abnormal<\/h3>\n

E6 means the control box isn’t getting a recognizable signal from the speed governor (pedal\/speed controller). Check the plug connection and inspect the coder wire for damage; replace the governor if reseating doesn’t help.<\/p>\n

E7 \u2014 Current Detection Circuit Fault<\/h3>\n

E7 points to the control box’s own current-sensing circuitry. Clean the circuit board of dust and lint, check that the power voltage is stable, and restart. This is a board-level fault rather than something fixable by cleaning a plug alone.<\/p>\n

EA, Eb, EC & Ed \u2014 Over-Current, Voltage, and Brake Faults<\/h3>\n

These four are all power-supply and braking-circuit protections: EA is a hardware over-current trip, Eb is system over-voltage, EC is system under-voltage, and Ed is a brake resistor protection fault. For Eb and EC, cut power immediately and check that your supply matches the rated 220V rather than continuing to restart the machine repeatedly.<\/p>\n

A Different Family: JACK JK-T781E Bartack\/Pattern Machines<\/h2>\n

If your machine is a JACK electronic pattern or bartack machine (the JK-T781E series), it uses yet another distinct control system, with its own six documented codes: E1 (power module error \/ abnormal over-current or over-voltage), E3 (stepper motor communication abnormal), E6 (stepper motor sensing abnormal), E7 (loose plug, position signal fault, blocked head, or heavy fabric), E9 (positioning signal abnormal), and E11 (needle signal can’t output at startup \u2014 often a faulty positioner inside the control box). These share some letter-codes with the C4\/E4 overlock scheme above, but the meanings are different machine-to-machine, so match the code to your actual model family before troubleshooting.<\/p>\n

Maintenance Tips to Prevent Repeat Faults<\/h2>\n