I am assuming it is a Euro model, since it is a 84' 380SEL? (I am thinking that the US version of the 380 was only in "SE" and "SL" models for 84'-85'. 380SEL for 83' and back? I am asking this because I am wondering if it still has the button controls or the turn knobs? I may be wrong and they all have buttons by 84'?

It could be that module in the unit gone bad.