(Home) Compass. Missing part

I have just purchased a 2lt T,Diesel 4wd townace (1989). Behind the drivers seatin the roof is a square hole cut into the headlining. Can any one tell me what is missing? Is it a coutesey light?
Also in the row of warning lights on the dash I have one that remains lit all the time. It is the one on the far left of the row, it shows 4 wheels and poss a diff(?) symbol in the middle of them. The vehicle is not in 4wd so what is it.
Thanks for the help
Steve - (#1298) Steve Taylor, 27 Oct 01

Steve,
From the Toyota parts illustration, this is where the "Magnetic Field Sensor" is fitted. I have one on my Masterace. I have a compass so, I assume that this device is something to do with that (I'm probably wrong). However the Toyota part No for the sensor is 89641 and,if you have no compass & inclinometer fitted (on the dash in front of the passenger seat) the sensor is probably not required and has been removed. Ref the 4WD symbol, this might be a minor malfunction of the 4WD selector switch. Others, I am sure, can answer this better than I can. - (#1302) John Davis, 28 Oct 01