I have a 1988 MCI 102a3 6v92 ddec II.
It has factory cruise, but has never worked for me, anyone know of any known problems or where to start with these?
On the DD engine the cruise works off the ECM. You have a switch on the service brake, clutch and parking brake. These are the first place to check when not working. If you don't have a wiring diagram I can send you one.
Jack