Cadillac Repair: 1999 Cadillac Sedan Deville Heater, heater control valve, diagnostic scanner

Question
Where is the heater control valve located on this car? Thanks.

Answer
There are 2 damper door control modules one on the drivers side and one on the passengers side and it requires the use of an expensive diagnostic scanner that can override the module to see if the module is faulty or not, As you have to remove half the dash to replace the faulty module.