Inside of Headlight Glass Dirty. Cleaning Ideas Please.

[PaulG]

Hi all, I searched but did not find so wondered if anyone else has experienced the above please?

I got an MOT advisory yesterday that my headlights have 'poor beam pattern' and looking at them the insides of the glass fronts (lenses?) is filthy.  Has anyone else experienced this issue please, know what causes this please (I suspect damp gets inside them and festers), and/or had success in cleaning them please?  Tips for cleaning methods most welcome!

Many thanks, PaulG

[cobblers]

I've cleaned quite a few sets of inner lights (which always seem to fog up a bit) very successfully by half filling them with warm soapy water (washing up liquid) and shaking them around for a few minutes.
Very thoroughly rinse, use an airline to blow as much water out and dry them on a radiator or in the oven at 60c

[PaulG]

Thank you Cobblers, it sounds like it might be a common problem!  PaulG.

[JeffRoo]

This might help? https://youtu.be/SOWX2yxaKSk?si=4b_1nqPSBnyxaASh
 

[PaulG]

UPDATE:  Thanks again Cobblers and also JeffRoo.  I'm liking the GoWesty video!  However, I'd already had a go at the 'Cobblers Method' this morning, and WOW! what a difference.  The lamps have just come out of the oven and look at least 90% better.  I tried to fashion a 'Giant Cottonbud' out of a rag and some stiff wire (which would have been an attempt to do what GoWesty's brush did) but was scared of scratching the lamp lens on the inside, but the hollow metal handled brush with a bend in the handle (as in GoWesty method) would be the way to go.

I added an extra step to Cobblers method, which was to shake out as much water as possible, and then pour a capful of Meths into the lamp, swilled it around quickly and poured it out, then repeated this step.  Then I blew warm air from a hair dryer into the headlamp bulb socket, and this comes out of the sidelight bulb socket with the Meths fumes.  Once 'Meths free' the lamps went into the oven at 50 deg C for 30 mins, and Hey Presto!

As a bit of an aside, the MOT was yesterday, which it passed with just this one advisory.  However, stripping down the headlamps this morning I found one of the sidelight bulbs dead!  Did it pass with a dead bulb, or did that blow on the way home yesterday, in the pouring rain, with the lights on?  We will probably never know!

Thanks again, PaulG.

[Mocki]

With regards to the side light bulb, if the engine was running whilst they checked the sidelights on a late van chances are the headlight bulb was on “DimDip” where the headlight bulb is on in the sidelight position whilst the ignition is on . If its a early van , the maybes it expired on the way home, maybe he didnt see it

[mike the van]

I did the same a while but drying off one headlamp in the oven, found the glass came away from the bowl, so maybe Hella/Bosch used a heat sensitive glue ??? Sods law the other wasn't shifting, but with glass off got it back to looking like new, with a polish with a soft duster. I think I siliconed the glass back on, hope so rather than the no going back araldite option!

Mike