Hi all, went into my local ATS for some new tyres and a couple of bulbs a few days ago and now I have one headlamp fogging up constantly.

These are a new pair of headlamp units and I specifically asked them to be careful as they were purchased because the caps were missing or broken on the old ones and they were obviously always full of moisture.

It turns out the smaller of the two caps on my nearside unit was not replaced at all but just left loose behind the headlamp. They advised me to dry it out with a hair dryer and replace the cap.

Well I spent much of Friday afternoon with a hair dryer and cleaned out every drop of moisture, replaced the cap, checked it was a good fit and this morning... It's all fogged up again..

Could anyone advise me of the best way to clear up this problem, the garage in question seem to think they have no further responsibility now they've refitted the cap...

Many thanks.....

How much fogging are you talking about - the whole lens or the bottom corners? A small amount is normal as the headlights have ambient air in them which does have some moisture in. As soon as you put the headlights on for a few minutes this will disperse.

If it is the whole lens then I might try some bags of desiccant to soak up any humidity. Alternatively you could run with the cap off and your lights on while the weather it is dry, and then put them back.

Ok, thank you for the reply, I've removed all the moisture several times now but it always comes back overnight even with the caps securely fitted. It's kind of a light misting over the whole unit....

The best way of de-fogging headlamps provided the rear covers fit and seal properly is to leave the car facing the sun on a hot day with the covers off. After a couple of hours, before the temperature drops, put the covers back on.

 

rotodiesel.