We have an old Kenwood Kdc-4080r Cd Player/radio (the type with the detachable front panel). Sometimes it works for hours with no problem. On other occasions the CD player behaves very unreliably, spitting CDs out, making sort of 'thud' sounds etc. We thought it might be damp weather that causes the problems and on longer journeys when the car has warmed up and in dry conditions the player works fine. How do we know whether it's the actual unit that we need to replace or whether it's the wiring and contacts behind? In short, do we need to replace our CD player/radio?