My Saturn LW300 (3L V6) was just returned from fixing some front end damage. Now, the front panel of the auto air conditioning display shows a capital "C" instead of showing the temperature, like it did prior to the service. Did they forget to hook up something?

The Air Conditioner only blows hot air now. R134 refrigerant has been checked, and pressure appears to be normal.

If anyone has any ideas, it would be much appreciated. I want to avoid a big repair bill if I can.