I have a 2007 s40 and I wanted to upgrade the bulbs to led but have been told by a volvo mechanic that the volvos don't like led bulbs that they bring warning lights on not bulb failure ones but other ones is this true

 

The brake lights, 4 rear parking lights, and low beam headlamp bulbs in most Volvos are monitored by a bulb failure system. Most commonly the system compares the current each brake bulbs use. If one is out - it will use no current - so bulb failure indication. Same for the other bulbs it cares about.

Led bulbs use very little current and tend to confuse the bulb out system.

BTW only you will notice the cool new led bulbs - but i understand why you might want to spend hard earned money on stuff like that - I've done it many times.