Land Rover Repair: transmission oil temperature light on 99 disco, disco 99, gearbox oil

Question
thanks once again. When i turn my disco 99 on it only takes about a minute and the Transmission Oil Temperture light illuminates. A while back it use to take quite a bit longer, and it would'nt in cold weather. I had taken it to somebody awhile back and they checked and changed the gearbox oil, and mentioned the oil looked brand new, it wasn't burnt looking.I've been hit by the recession and am looking for a do it yourself deal. but it is what it is. There might also be a leak in the back air shocks. but only sometimes, i don't know if it's connected. Pleease help Ben

Answer
There is no way that your Rover's transmission fluid can go from cold to overheated in one minute.  If your statement is accurate with regard to time, the only explanation is that the switch has failed.  The switch is located in the line to the cooler