the SD library default CS pins is 4
@neiklot thank you for correcting me
@neiklot thank you for correcting me@Soja call SD.begin() in setup()
when I had this problem the sketch I was running was too big for the UNO. it ran out of memory and got twitchy when I added SD. it had nothing top do with SsD, it just happened when I tried to add it.Soja, please read How to use this forumpay particular attention to 7. If you are posting code or error messages, use "code" tags
what memory usage prints IDE after compiling the sketch?