Our family does a lot of towing on and off the farm. Dust, dirt, mud and water get into the towing connections from both the front and rear of the male and female plug connectors. While removing the last lot ready for replacement, I was also doing some glue gun work for the kids. The attached pictures are what resulted.
After connecting the new cable to the plug, you will notice that the makers of some of these plugs have the cable entry cutout right in line with one of the screw holes. Make a new cutout by filing the aluminium with a round file between two screw holes (1). Fill the entire rear hollow part with glue; it takes exactly 3 sticks. After it has cooled, turn it over and hold the lid open (I used 2 kg hammers to do this) so that you can carefully fill the flap flush with glue.
Now comes the tricky, or tacky, bit. Wait for about 2 minutes and touch the glue to make sure it is not too tacky, but pliable. Then, press the lid down to make a depression and quickly pull it back (2). Do this a few times, so that the lid does not get stuck down. Once dry, it makes a good seal (3).
The procedure I have outlined covers the glue-filled female cap that is fixed to the vehicle. The fixing holes must be drilled out to hold the screws, of course.
Do the same for the male connection. Once the cable is connected, pull back the rubber gland and fill it with glue right up to the brim, even letting it overflow a bit. Then press the rubber gland over the hot glue.
Voilà… no more hassles with connectors when towing or caravanning.