2000 W900L Weak Heat

Hi all. I have a 2000 W900L Kenworth. I'm having troubles with the HVAC system. When I turn on the heater in the cab, it blows very weak out of the vents. Also it doesn't get as hot as it should. In the sleeper, it blows strong exactly how it should, excpet it also doesn't get as hot as it should. I had Loves replace the blower motor and the resistor for the cab but no luck. There are no leaks around the box near the firewall. The squirrel cages are in correctly. Any ideas? Heater hose? Actuator?

Thanks

 

Yes we checked all the valves. They appear to be all the way open. The technician at Loves said something about an evap system being clogged.

 

Yeah all the buttons on the dash work. I can feel the air switch from the floor to defroster, etc. Its the same amount of air flow in each vent. I was thinking maybe it's an actuator, but I'm not sure because the flaps work. I can hear the blower motor working how it's supposed to but when I go inside I feel something restricting the air flow.

Also the AC in the sleeper blows strong how it's supposed to, but it's also not as hot as it should be

 

I just checked the ac compressor with the tech watching. Its not that. It's working how it's supposed to

 

Something is definitely clogging the system. Guess I'm going to have to stop by the dealership