I am looking for technical support.
Hopefully I have the correct web-site.
I have a 2005 Volvo S40 AWD T5
The low beams have always been pretty weak.
It's like the daytime running lights, when it gets dark, don't get any brighter.
Is there some kind of light sensor in the car that increases the brightness
of the low beams when it gets dark?

 

I have the same problem with my 2005 s40, high beams are great but low beams are very dim.

 

I might be mistaken on this but I am pretty sure the bulb intensity is the same day or night. At least that is what I was noticing with my own s40. I recently cleaned the lenses on the lamps and swapped the halogen bulbs out for some LED's. The headlights are still not quite as bright as I wished them to be, but what I am looking for isn't very kind to other drivers so I stuck with this solution. I eventually will add some fog lights to help since my trim didn't have them included.

These are the LED's I used:

This video has been pretty useful for cleaning the head lamp lens.

 

Ditto same problem.............

 

They are dim. Buy the brightest bulbs you can afford. The price goes up with the brightness unfortunately.

There are issues with the aftermarket HID solutions. I wouldn't go there without high DIY skills.

The LEDs are bright as hell but somewhat short range. More of a glow than a focused beam. But super white light and very bright. Reflective objects like stop signs will glow from a distance. Kind of cool.

EDIT: Forgot to add, if you go the LED route, get the ECM friendly versions. The non-ECM friendly will start to flicker in a very short time. Volvo uses Pulse Width Modulation on the headlights and LEDs do not like it at all.