SX70 exposure problem

Hi all!
Has anybody experience of what can be wrong with the light meter of a Polaroid Land camera SX 70? My camera always makes the same (long, let's say half second) exposure both in direct sunlight both in the dark... No difference moving the light/dark selector...
Confusing...

Does the shutter actually open for that long? I had a problem with my SX-70 where it took a while to take the shot, but it was always well exposed. It turns out that the capacitors were drained from years of non-use, and it took a while to get back up to speed. Another option if the photos come out well exposed is the battery being dead. Are you using Impossible or Polaroid film?

Hi Nick, and thank you. Yes, the shutter opens for that long and all the pictures turn out overexposed, also rotating the light selector to the darkest setting. I am using new impossible film (with a fresh battery of course...)