745 TD overdrive electrics components?

I have an electric problem with my 745 TD 1989 overdrive. Does not switch
reliably any more after about 1 hour driving. My Haynes manual did not give a
complete description of the electric components. So I have started with cleaning
contacts I could access and identify definitely to belong to the overdrive
circuits: contacts and pushbutton in the gear switch handle and contacts on
solenoid on overdrive down under the car. But shouldn´t there be still a relay
somewhere giving voltage to the solenoid and to the pilot lamp at the instrument
panel? Does anybody know where that relay is located, if there is one?

Thanks for any input!

 

On the 240 series it is under the dashboard next to the glove box. The
ones I've seen were a sealed unit, so replacement is the only option.
My guess is that it is in the same place on the 7 series cars.

It should look like this but the color may be different:
http://www.theautochannel.com/autoparts/images/engineparts/q098976002svo.jpg

Typically relays either work or they don't and they don't cut out
intermittently, but that is a good place to start. The next place I
would look is at the wiring running from the shiter to the overdrive
unit. Years of flexing may have caused a break in one or more wires.

 

http://www.swedishbricks.net/faq/transod.html#jumping

 

Excellent and very detailed information! I'm sure the O.P. thanks you.

 

The relay is located behind the ashtray in the central electrical unit.
Remove the cover over the cigar lighter and the two screws behind it and
move that section of the center console out of the way. The relay is on
the right side of the relay rack. The relay will be white, orange or red
depending on whether it has manual or automatic transmission. If it is
manual be sure to ensure that the fourth gear switch on the top right
hand side of the transmission is providing sufficient ground to allow
the OD relay to switch correctly.

Bob