No overdrive

Have recently purchased a 1988 760 2.3 turbo manual + overdrive estate with 153,000 on the clock. I did'nt realise the overdrive was'nt working until I was on the way home. My fault entirely as I should have checked it before handing over the hard earned!!. On phoning the bloke I got the expected reply that 'it was working when I last used it'. On replacing the fuse (no. 14 - 10 amp) the fuse blows as the ignition is turned on. What I can't work out is why the electric windows and sunroof still operate OK even though they are protected by the same fuse (according to Haynes). My (limited electrically!!)mechanic has had the thing for nearly a week and is not getting anywhere. Any ideas?.

could be the overdrive solenoid?

Overdrive relay? M46 in relay compartment behind fuses. Also check gearbox connections at solenoid. Sounds like a short somewhere though due to fuse blowing on ignition switch on. Ali

Fed up with it !! 

Thanks to the two above that replied to my query - but my mechanic has now given up on it as he is not getting anywhere. Nothing apparently is where it is supposed to be (wiring wise) and something is still blowing the fuse. He did manage to get it working half a dozen times but does'nt last very long before it blows again. Will be trying to sell the thing as it is, just to get it off my hands and will therefore bring to an end my very brief but last relationship with a Volvo. Long live Mercedes.