Owing to their similarities, motorhomes and caravans usually share the same window manufacturers. Some of the most well-known are Dometic-Seitz, Heki and Fiamma.

However, older ‘vans (like mine) were fitted with windows made by a company called Birkholz, which has long since ceased manufacturing them.

A quick look at online forums will highlight the problems this causes when trying to source replacement windows (size compatibility with current ranges) and spare parts.

Catch operation

In the main, these windows are quite robust and give long service, but those fitted to my motorhome are of the three-point catch variety, using one central lever to operate all three catches simultaneously.

To do this, the lever drives a PVC strip in a channel which, in turn, moves the left and right catches.

As already mentioned, the activation strip is made from PVC, and those of you with an understanding of plastics will know that PVC has an Achilles heel – it can become brittle over time.

Added to that, when PVC is cold, its malleability decreases, making it more likely to fracture.

This article details the replacement of the PVC with nylon, which has better thermal/ageing characteristics, coupled with good self-lubricating properties that enable it to slide more smoothly in the guide channel.

The nylon I’ve used here is Nylon 6, procured from a wholesaler (Amari Plastics, although others are available). I bought a complete minimum-order sheet (1m x 2m, 1.6mm thick) because trying to buy strip with the dimensions required is non-viable. And, although buying the whole sheet cost me £42, it has enabled me to repair the five windows in my motorhome at an average cost of £8 per window (with quite a bit left over, too). An aerosol can of PTFE will also be needed.

Procedural tips

  • The old PVC, as explained above, is highly likely to be brittle and might break even more when being removed. This is undesirable if it can be avoided, because the PVC has to be used as the pattern for cutting the new strip. Heating it with a heat gun or hairdryer will make things easier.
  • When cutting the new strip of nylon, it is essential not to go oversize – it is very difficult to remove any excess from the side of the strip once cut.
  • Check that the new strip will run smoothly in the channel before cutting the apertures.

Tools required

For this job, you’ll need a marking gauge, craft knife, shears/scissors, Torx screwdriver and various items from any conventional tool box.