The problem with my digital wrist monitor is that it doesn't exert enough pressure on the bracelet and immediately indicates error U which is "insufficient pressure". I already disassembled it and I did not find fault at least in the compressor that starts and works and I also tested the air chamber is not broken, I do not know what it is, another element connected to the hose-manifold that receives compressed air and takes it to the chamber and the electronic card.