NO HEAT on 1999 Jeep Grand Cherokee

Heater not working-blows but cold air
AC works fine. Dealer told me it needs MID case and REC case. What are those items? Any Help

Asked by for the 1999 Jeep Grand Cherokee
Did you pay for the dealer to check out your Jeep? If so I would asked what does mid & rec case mean. I believe mid case means you mhave a broken blend door. There is a aftermarket blend door available. If your dealer doesn't decode his terms I'd find some good independant repair shop. On the REC case no clue. maybe someone will know that term. Good luck