Volvo Repair: 1990, 740 Volvoauto trans with no Overdrive, shifting into overdrive, volvo auto

Question
My 1990, 740 Volvo, non turbo, with auto transmission, all of a sudden quit shifting into overdrive. Pushing the button on the shift lever will cause the relay to click and light on dash will come on.

My question is how do I test at the transmission?
Thanks,
Bob

Answer
Hello Bob,
     My first choice of answers includes...overdrive relay  
is faulty.
         next...trans. has dirty fluid and is unable to operate properly.
          Volvo auto trans are very sensitive to fluid type and condition of its fluid...most trans failures are directly related to fluid problems..
            Be sure fluid level is proper.
     Trans shift cable is out of adjustment...or broken?
      
             Good luck Robert     

                Bilbo