AC/Heater Control Unit on 2002 Volvo S40

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Air was constantly blowing, unable to turn it off. Can't adjust the speed or level which air blows. It will produce cold air when on AC setting and will heat when on the heater setting. Now it is not blowing at all. Can control unit be repaired cheaply with a resistor. If new control unit is required, what is the difference in a unit with or w/o DSA? What does DSA stand for?
(1) Answer
A diagnosis will be needed to determine what the problem is. There are a few possibilities, the main module and the blower motor module. It's possible the blower motor is bad now too.
I'm not sure what DSA is, did you see that in relation to the A/C control module?