Hello, I have an 02 2500 that blows lukewarm air. I flushed the heater core and the blend door appears to be working, when i shift from cold to hot it goes from cold to lukewarm. I believe there is probably some debris and other gunk in the HVAC box causing it to not blow warm. Is it possible to clear this out without removing the whole dash? If so any ideas how to remedy this or if it could be something else. Thank you