---
title: How do I perform a function check?
description: To ensure that your coupling system operates correctly and remains road-safe, regular function checks are required. This checklist provides a quick and clear overview of what should be inspected – directly in operation.
image: https://blog.vbg.eu/hubfs/VBG_Norway_-6804-1.png
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Published on 28 May 2026 by [Emil Vikingsson](https://blog.vbg.eu/en/author/emil-vikingsson) > 4 min

# How do I perform a function check?

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How do I perform a function check?

4:32

*Summer and the vacation we all look forward to are just around the corner. No matter how you plan to spend your time off, it’s reassuring to know that your truck equipment is in good condition when it’s time to get back behind the wheel again.*

All moving components, or those exposed to harsh environments, require some form of maintenance. Most often, this means cleaning and lubrication.

Below, you’ll find checks you can perform yourself using a wear gauge, torque wrench, and a little VBG mechanical oil to ensure that the coupling remains in good condition both during and after the summer.

## How do i perform a function check? 

To ensure that your coupling system operates correctly and remains road-safe, regular function checks are required. This checklist provides a quick and clear overview of what should be inspected – directly in operation. 

This places high demands on both people and equipment.

## Check coupling wear

Start by checking the wear on the coupling. Measure and ensure that the values are within approved limits:

**For VBG 750/795/795VR:**

- A-dimension: max. 45.7 mm
- B-dimension: min. 42.5 mm
- C-dimension: min. 55.0 mm
- Check that the wear indicator marking has not been exceeded

**For VBG 760:**

- A-dimension: max. 49.5 mm
- B-dimension: min. 44.8 mm
- C-dimension: min. 55.0 mm

If the values deviate from the limits, components need to be replaced.

## Checking the locking pin and cab signal

An important part of the function check is ensuring that the locking pin and signals operate correctly. For air-assisted couplings, it is a legal requirement that both red and green signals are visible to the driver.

**With the coupling open:**

- The locking pin should protrude and show red
- A red warning light should be displayed in the cab

**With the coupling closed:**

- The locking pin should be retracted
- A green light should be displayed in the cab

Incorrect signals may indicate faults and could cause accidents, for example due to improper coupling. Contact your workshop for further troubleshooting.

## Visually inspect components

Carry out a thorough visual inspection of:

- Drawbeam
- End plates
- Drawbar

Look for cracks, deformation, or other damage that may affect safety. Jackknifing and over-angled coupling are the most common causes of this type of damage.

## Ensure correct tightening torque

Check that all fasteners are tightened correctly:

**Drawbeam / End plates:**

- M14: 163 Nm (10.9)
- M16: 250 Nm (10.9)

**Drawbar (Multi / Multi XF):**

- M14: 125 Nm (8.8)
- M16: 195 Nm (8.8)
- M27: 600–650 Nm

## Check the drawbar eye wear

Finish by checking the drawbar eye:

- D-dimension: max. 59.5 mm
- T-dimension: min. 19 mm

If the limit values are exceeded, the drawbar eye must be replaced.

## Lubricating the coupling

Regular lubrication is important to ensure proper function and should typically be carried out once a week. 

## Summary

A function check is quick to perform – but crucial for detecting wear and safety risks in time. By following the checklist regularly, you ensure that your vehicle combination operates as intended, every day.

 

[![Download VBG’s simple checklist](https://no-cache.hubspot.com/cta/default/2640104/003bf25f-4cea-4424-97b8-34f73774312f.png)](https://cta-redirect.hubspot.com/cta/redirect/2640104/003bf25f-4cea-4424-97b8-34f73774312f)

 

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#### [Emil Vikingsson](https://blog.vbg.eu/en/author/emil-vikingsson)

 Emil is a customer advisor at VBG, and if you've ever had a question or query about our products, chances are you've been in contact with him. With many different driver titles and 13 years in the industry, he knows what works in practice. He comes from the west coast and prefers to spend his free time with his girlfriend and dog. The rest of his time is spent with training, friends and the summer place.

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