Defective gas strut passenger seat

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A defective gas strut on the driver's or passenger's seat is noticeable by the seat constantly dropping when under load. This is usually caused by a leak and the resulting oil leakage. Not everyone is particularly fond of the Bowden cables that lock the gas strut, which is why the defect can also be seen as an opportunity to get an electrically height-adjustable seat.

How to carry out the conversion is described below.

Removing the gas strut

The seat is raised to its highest position and fixed in height with wooden blocks, for example, or preferably a suitable piece of wood. Ideally, the seat should be supported at all four corners. The middle should remain free, as the installation situation is already cramped and therefore not ideal.

First remove the Bowden cables. Then loosen the lower and then the upper screw of the gas strut on the seat frame. If it is under tension and cannot be moved back and forth easily, the height of the supporting elements must be adjusted accordingly.

As soon as the desired loose status is reached, the two screws can be removed and the gas strut, which is tension-free in this state, can be safely removed.

Choice of servomotors

As known from electrically adjustable seating or bed furniture, servomotors / linear actuators ensure the positioning of the respective furniture parts. These are available in various sizes, stroke lengths, load capacities and speeds.

Despite this supposedly extensive selection, the range is significantly reduced if the given, unchangeable installation conditions are taken into account.

Hardly any Suitable drive to choose from, with the exception of the one in use here, which is designed to lift 326 kg (1,500 Nm).
Since I tend to be skeptical of such information, I decided to use two of these drives, which results in a real load of < 25 % and the material stress is therefore far below the 50 % that is usually calculated.

Unfortunately, the built-in limit switches cannot be used as they are not adjustable, so you have to use your own feeling, especially for the lower position, as a substitute limit switch.

Installing the drives

The drives are attached to the brackets provided on the console using two V2A 90 mm M6 Allen screws and two self-locking V2A M6 nuts, as well as suitable spacers (to prevent uncontrolled sliding back and forth), first at the top and then at the bottom.

Electrical connection of the drives

It is operated via a rocker switch with neutral position attached to the console, which reverses the polarity for the up and down movement.

The cable routing must be carefully planned to prevent the cables from jamming or being cut by the scissor-like movement of the seat console when driving up and down. Once a safe position for the cable route has been found, cable ties should be used to secure it.

One drive with a nominal 2.5 A can be fused with 3 A, both drives with 7.5 A.