Front defroster not blowing 100% on 2005 Volvo XC90

2005 XC90 front defroster just started blowing at about 50%. Took it to dealer who said there were not diag codes and it appeared to be working. It is not working, it takes about 20+ minutes to defrost the car - when it used to blow hard air and clear almost immediately. He compared it to some random Volvo's (newer) he had sitting around and said "see, they all sound like that", til he got to one close to our age and it blew hard like ours used to. What could be the problem here?

Asked by for the 2005 Volvo XC90
poss cabin air filter is plugged?
Where can I check that?
under glove box should be a trap door
Those sneaky cabin filters.......
Having air filter looked at today, but new symptom. Turned on defroster, drove about a mile and it started blowing 100%, then about a minute later back to 50% and blowing at me through center vents. It has never blown center while on defrost... Would that still be an air filter problem? It seems to have a mind of it's own now!
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1 more answer , 1 more comment
Possible vent door actuator not swithing to that HVAC vent. Do you have the same lack of power on ac or heat where the fan does not seem to blow on certain settings? If so, blower motor resistor issue.
Only defroster with issue