I have a 2000 dodge caravan and the rear heat works great but the front heat blows cold?

The blower motors all work fine, has new water pump and brand new coolant. The top vents in the dash blow lukewarm warm but if you switch it to defrost it comes out ice cold but the rear heat still blows super hot air. Coolant level is full.
I ve read about the blend door could that be the issue? Could a coolant line to the front dash be clogged? I m a ford mechanic but kinda stumped and have never worked on a dodge.

Thanks in advance

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