I took my truck to the shop to fix the ac its been there 5 times and it still doesnt work like it should. Well now i have no heat. The little valve that lets the water run threw the heater core dosent move. I can move it by hand but it still doesnt seem to get hot in the cab. The valve that mounts right on top of the heater core in the cab makes noise but i dont know if its working right yet. Any thoughts on what to check?