One of the 'lexus style' rear light cluster on my fabia has a large star-shaped crack in it, but is not letting water through and isn't impeding the red or amber of the indicators or brake light. It's on the clear plastic bit to one side and has passed the MOT with it.

 

Just wondering what I can do to stop it from getting worse. I see a lot of different types of clear repair tape on amazon and ebay...just wondering if there's any particular brand you guys would recommend?

 

Since there isn't a piece of the lens missing, I'm not sure if I can use the filler-sand-polish technique...unless you guys advise otherwise?

 

Many thanks.

depends on how fussy you are re: looks   if not and you can get to the inside I would just "stitch" it with a soldering iron and then run some clear araldite along the crack lines 

Thanks for the tip and apologies for the delay. Hopefully I can open it without having to do the whole heat-in-oven thing like the front headlamps.

You can use dichlomethane.  It chemically welds most ridgid thermoplastics like PMMA, ABS and their friends and cousins.  Most rear lenes are PMMA or derivatives, ie acrylic.

My big bottle of "Tensol" was the same stuff but can't find it now.  Still available to buy last time I looked, but expensive.  Comes in "A" and "B", which is code for thick and thin, not sure now which way round it is.  You will find the thin more suitable.  The thick will build up enough to replace missing bits.  A good subsitute for this is plumbers plastic solvent glue.

Last time I needed some to repair a bit of fridge trim, I went to a decent model shop and they had something similar but with a brand name.

I used the thin to glue sheets of acrylic together to make a block.  Polish round the edges and you couldn't tell it wasn't solid.

It is very thin liquid, which will sqeeze into tiny gaps by capillary action.  Very carefully apply with a small artists brush along the line of the crack.  Hold (if it tends to open - use tape), until dry (a few minutes) and you should get a more or less invisible join.  Sometimes a few coats are necessary.  (do not stress the join until throughly "off", a few hours - not likely to be a problem in your case.

Both types dry by evaporating their solvent.  This is some nasty stuff as you will find when you open them.  I make sure the work area is very well ventilated.  Keep bottles properly sealed when not in use.  They are also inflammable and a skin irritant.  So be careful and wear gloves - actually I find them easy to work with, apart from the smell.

 

You get an invisible repair for about a fiver.  Read and mark the dangers and hazards.

Thanks, Nick. I'll look into that. Appreciate the detailed instructions!