Ergonomics and Risks in Wiring Harness Production

Wiring harness production safety: what does the hazard class bring?

A car's wiring harness is a product in which hundreds of wires, terminals and connectors are joined together largely by hand. Wires are cut and stripped, terminals are crimped, the harness is formed on an assembly board, taped and tested. Wiring harness production safety is therefore less about heavy machinery than about managing small movements repeated thousands of times.

In the List of Workplace Hazard Classes renewed in 2025, "wiring harnesses for vehicles" are in the hazardous class under code 29.31.04. The main obligations of this class are:

Obligation	For the hazardous class	Basis
OHS specialist	At least a class B certificate; at least 20 minutes per employee per month	Law No. 6331 Art. 8, OHS Specialists Regulation Art. 12
Workplace physician	At least 10 minutes per employee per month	Regulation on Physicians and DSP Art. 12
Basic OHS training	At least 12 lesson hours; within 3 months of starting work at the latest	2026 Training Regulation Art. 8, 13
Refresher training	Every 2 years, at least 8 hours	2026 Training Regulation Art. 14
Periodic examination	At least every 3 years	Health surveillance legislation
Risk assessment renewal	At least every 4 years and on changes	Risk Assessment Regulation

The primary text of the training provisions is in the Official Gazette. You can calculate the times for your headcount with the OHS obligation calculator. We compared the classes of automotive and metal activities in our article on hazard classes in automotive and metal.

Posture at the wiring harness assembly board

Wiring harness assembly is usually done standing at large, inclined assembly boards. The operator places wires on the forks on the board, walks from one end of the harness to the other, and tapes and clips. Three things cause problems: the height and inclination of the board, reaching to distant points, and standing on a hard floor all day.

Height and inclination: The board is adjusted to create a working zone close to elbow height for most employees. On lines where operators of different heights work at the same board, a height-adjustable board or platform should be the first choice.
Reaching: If the shoulder is raised and the trunk bent forward to reach points at the top edge of the board, the board inclination is changed or the operation in that zone is moved to another station.
Moving boards: In rotating or conveyor-based board systems, the operator waits for the board to come rather than walking. This reduces the walking load but may increase time pressure; ergonomic load is also taken into account when setting the line speed.
Floor: At standing stations, anti-fatigue mats, suitable footwear and sit-stand stools for short sitting breaks are considered.

For the effects of standing work, see our article on the risks of standing work.

Wrist strain: wrapping tape, pushing terminals, fitting clips

In wiring harness ergonomics, most complaints come from the wrists and fingers. The reason is not the weight of the movement but its frequency and form:

Wrapping tape: When tape is wrapped around the harness, the wrist repeatedly rotates and bends sideways.
Pushing terminals: Pushing a crimped terminal into the connector cavity requires applying force with the fingertips. With small connectors, the grip is a fingertip pinch, where force is hardest to apply.
Clips and ties: Plastic clips are pressed into place with the thumb.

Measures against wrist strain:

Tools: Tape-wrapping aids, terminal insertion pens and connector holders are used.
Job rotation: The same operator does not only wrap tape all day; rotation is planned between tasks that use different muscle groups.
Micro-breaks: Short but frequent breaks are more effective than long and infrequent ones.
Material information: The terminal insertion force of connectors is requested from the supplier; this information is used in station design and job rotation.
Early reporting: Complaints of numbness, tingling and night pain are reported without hesitation.

Crimping machines and cut-and-strip machines

A crimping machine is a press mechanism that compresses a terminal onto the end of a wire. The closing zone of the applicator is a crushing point for fingers. Automatic cut-strip-crimp machines contain blades, feed rollers and moving carriers.

Basic rules for crimping machines:

The guard in the applicator area is kept in place so that fingers cannot reach the crushing point. Opening the guard to make wire feeding easier is the most common mistake.
Changing the applicator, setting up and removing a jammed terminal are done after the machine has been isolated from its power. On pneumatic machines, compressed air must also be released; lockout and tagout are applied for these tasks.
On automatic machines, cover interlocks are not bypassed; covers are not opened to reach inside while the machine is running.
Cut wire ends and scrap terminals are collected before they pile up on the floor.

Annex III of the Regulation on Health and Safety Conditions in the Use of Work Equipment lists mechanical and pneumatic presses among equipment subject to annual periodic inspection. Clarify with the person carrying out periodic inspections, based on the manufacturer's documents, whether your crimping machine falls within this scope. For guard design, see our article on machine guards.

Eye fatigue and lighting in quality control

The final check of a wiring harness is largely a visual and electrical test. At the test table, the operator plugs in connectors, reads the result on the screen and scans the harness by eye: a wire of the wrong colour, a missing clip, damaged insulation. Focusing on small details for hours leads to eye fatigue, headaches and neck pain.

Lighting: At the inspection station, adjustable, glare-free local lighting is used in addition to general lighting. For the measurement approach, see our article on lighting measurement and lux values.
Magnification: If a magnifier lamp or microscope is used for crimp inspection, it is positioned so the employee can look without bending the neck forward.
Screen: The screen showing test results is slightly below eye level and at an angle that avoids reflections. For the rules, see our article on working with display screen equipment.
Rotation: An operator doing continuous visual inspection switches to another task at set intervals.

Assessment for new projects and line changes

In wiring harness production, the product changes often: a new vehicle project, a new connector family or a taping pattern changed at the customer's request. The risk assessment is renewed when technology, equipment or production methods change, even if it has not expired. When a new project is brought onto the line, the following steps stop ergonomic problems being carried into series production:

Observing trial production: Every station is monitored in the first batches; operations requiring reaching, wrist bending and fingertip force are noted.
Board design: The assembly board is tried out with operators of different heights before it goes into production; problematic connection points are moved at the design stage.
Cycle time: When setting the line speed, not only productivity but also the number of repetitions and the rest allowance are taken into account.
Training: The new operation, together with its changed risks, is explained to the operator in practice; a training record is kept.
First-month follow-up: Complaints on the new line are monitored together with the workplace physician in the first weeks.

Material flow and other overlooked risks

There are risks beyond ergonomics too. Heavy cable reels are moved not by hand but with a reel trolley or lifting equipment. Crates for finished harnesses are stacked at waist height. Ultrasonic welding machines used on some lines carry noise and hand-crushing risks; stations where soldering is done need local ventilation for fumes. Cable offcuts and packaging waste piling up at the side of the line are the most common cause of slips and trips.

For businesses in the automotive supply industry in Bursa, customer audits also directly affect OHS arrangements. We explained the steps for preparing for an audit in our article on preparing for a supplier OHS audit; the sector's general risk and document list is on our automotive supply industry sector page. When preparing a risk assessment for assembly and quality stations, we observe each station and match the hand and wrist load to the steps of the operation.

Frequently Asked Questions

Which hazard class is wiring harness production in?

In the List of Workplace Hazard Classes renewed in 2025, wiring harnesses for vehicles are in the hazardous class under code 29.31.04. Your workplace's class is determined by the main activity code in your SGK (Social Security Institution) registration.

How is job rotation planned in wiring harness assembly?

Rotation is not between tasks using the same muscle group, but between tasks with different loads, for example wrapping tape and visual inspection or material preparation. The plan is written into the risk assessment and implemented together with the line leader.

What is the most common accident on crimping machines?

A finger entering the closing zone of the applicator. This is most often caused by opening the guard to make feeding easier or trying to remove a jammed terminal without isolating the power.

What should be done for an employee with wrist pain?

The complaint is reported to the workplace physician. After an examination, the physician may recommend a change of task, adjustment of the station or further tests. If similar complaints recur at the same station, the problem lies not with the person but with the operation, and the risk assessment is updated.