I have a 2 year old set of Wilma 4 lights and on most rides I get a small patch of condensation on the centre of the lamp.

On nights like last night, i.e. very humid, the condensation is about the size of a 10p bit. Enough light gets through to mean that it's not a real issue, but i can tell that I am losing light as the patch develops during the ride.

On turning the light off, the condensation subsides quite quickly.

Have tried taking off front cap and "drying" out the lamp and whilst this often improves it for a couple of rides it always returns. I have also tried "visor spray" and again it does improve things slightly but does not eradicate the problem.

Any thoughts?

It happens even on the betty's but output is not effected. Best just to take off the lens cap after use or could use plumbers tape round the seal….

Thanks. Good to know that it is not just mine.

I assume that it is just due to the large temp difference between the air inside the lamp and the ambient air. Plus the air in the lamp will always have some mositure in it, as unlike a bulb it is not sealed/filled with inert gas etc.

Have already tried the plumbers tape option and doesn't seem to make much difference.

The only thing I can think off is trying to make sure that the air that is inside the lamp unit is as dry as possible. But even then I'm not sure the rear of the lamp is totally hermetically sealed and thus over time some moisture will get back in.