Adjusting device for a seat and method of operating an adjusting device

An adjusting device for a seat comprises at least one fluid chamber (2, 3) and a valve assembly (15) in fluid communication with the fluid chamber (2, 3). Each fluid chamber (2, 3) is configured to be installed in the seat (1) to adjust at least a portion of the seat (1) upon inflation or deflation. The at least one fluid chamber (2, 3) comprises a first fluid chamber (2). The valve assembly (15) comprises a check valve (16) and a 3/2-way valve (17). A first port of the 3/2-way valve (17) is in fluid communication with the check valve (16), and a second port of the 3/2-way valve (17) is in fluid communication with the first fluid chamber (2).