Hello, I am living in Finland and I have a problem with the heating system.

When I start the car at low temperatures the blower is working ok. i can change the position to defrost and everything. the system starts to get warm abd I have the feeling everything works fine. After driving apprx. 30 minutes the blower is still running but the air intake is getting lower and lower. after a while it is really cold inside of the car and I have a feeling that the heating system is not working at all. I checked the air duct if it is blocked but everything is fine!
could it be that there will be some ice if A/C is running for defrosting an than there will be blockings?

I appreciate every kind of help.

Thanks Thomas

 

heres my question have you changed the thermostat?