Volvo Repair: 1991 volvo LD, automatic transmission, liar

Question
i have an 1991 Volvo with a automatic transmission, ad the problem is the over drive will not turn on or click in. there are no sign's that point to a relay problem.
  the person that sold me the car said that, " there is a switch that has to be replaced in the engine area?  

Answer
Daniel, That person is a liar.  You need to determine if its kicking in or if you are going 65 MPH and the thing is cranking 4000 RPM then there is a problem.  Usually is a relay or solonoid problem.  Does the arrow on the dash go on and off when you push the button on the side of the shifter?  Roger