what would cause no heat in the passenger compartment

Hello, so your driverside air vent is blowing hot air but the passenger side is not. That is most likely the A/C vent door is either broken or non operational. The vent door is operated by a vacuum hose to open and close when you change temperature as well as air flow settings eg. (Face or floor for feet). Double check the condition of the vent door which is located on the evaporator box under the passenger side of the dash. If it is in good condition check the vacuum hose to make sure it is snug as well as no cracks or tears. Replace as necessary. Hope that helps. Cheers!, Brandon