1990 740 gl on going saga

I have replaced temperature sender but still have fault code.
Old and new sensors have similar resistances.aprox 4.6k ohms near
freezing and 210 ohms near boiling.So maybee it is a cable fault but as
I haven't found the computer yet and have not got a wiring diag.can't
test. Computer may be near glove box but have not figured how to remove.
Car is right hand drive.

Also can any one tell me what is the black thing attached to the left of
the receiver drier? (I can see that it has been leaking)
It seems to have plastic cover over hex thingo but I don't want to
fiddle till I know what it is

http://picasaweb.google.com/FMurtz9/ReceiverDrier

 

It is how the AC is charged from the factory

 

What happens if you undo the black hex thingo? is it just a cover or
does it vent the refrigerant?

 

It has a valve similar to a tire air valve, you can remove the cover and
not lose refrigerant.

The computer on the LHD cars is on the right side wall just ahead of the
front passenger door, the cover on the side has a bulge under which the
ECU is mounted. I'm not sure where they put it on RHD cars, but look at
the side panels on each side and see if they're both the same thickness.

 

Thanks.