You are going to have to find someone with a code reader that can read Volvo specific codes. A dealer might be a logical place, just do not agree to service if the price is over your budget. A 'new' DIM could be a possibility for the fuel sender, but so could a cracked wire reacting to temperature changes.
The new ECC units have me somewhat baffled. It could be the unit itself, the temperature knob, or a vent damper. A scan will push out error codes.
EDIT:
http://www.matthewsvolvosite.com/forums/viewtopic.php?f=9&t=41547
http://www.volvoxc.com/forums/showthread.php?15475-Dual-climate-control-acting-up
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