Volvo Repair: Climate Control, volvo 850 turbo wagon, automatic climate control

Question
1994 Volvo 850 Turbo Wagon.

Problem: The automatic climate control function does not work. It does not activate the fan or temperature control for the A/C or heater.All A/C and heater functions do work in the manual mode. What would cause the automatic climate control not to function?  

Answer
Hello David,  The problem lies in the actual 'control head',control panel.There should be 'codes' in the diagnostic memory.The dealer is the only reliable repair source,many cases after-market scan tool a/c function is an option package,they may not of purchased.Thank You and good hunting!  PKD