2 double insulated light fittings on 1 switch?

[ToneEQ]

I've read through the Wiki and I know it possible to have 2 lights operated by one switch, and I've checked the wiring and it's the same as this: //www.diynot.com/wiki/electrics:lighting:parallel (minus the earth cables as the fittings are double insulated).

Would this cause any issues with double insulated fittings? The reason i ask is because one of the fittings keeps over heating (the second one from the switch). The plastic components inside have changed colour from a white to a dark yellow/brown cover, but it works fine without the diffuser fitted over the bulb (bulbs being used are 40w and the fittings state 40w maximum).

Obviously it's not safe so I not using it at the moment, but if I'm going to replace the fitting would the same happen to a replacement double insulated fitting?

 

[Chri5]

What do you think the diffuser does ?

On a light it tends to be there to reflect both light and HEAT away from the fitting. Please take a picture showing us the issue so we can be clear what the heat damage is like.

 

[ToneEQ]

1st light from switch (no problems with this one)

2nd light (plastic is broken because the heat stuck the cover on, removed to check wiring)

 

[Taylortwocities]

It is obviously because the plastic above the lamp is not up to the heat from the lamp.

I would return the item to the maker for a refund. This assumes you have followed the makers lamp wattage and type. Like you used a candle shaped lamp if that is what is specified.

Your problem is about to be solved as you will not be able to buy tungsten lamps any more . Low energy ones run much cooler