* Blend Door Actuator (Passenger Side): This is the most likely culprit. The blend door actuator is a small motor that controls the flow of hot and cold air to different vents. If the actuator for the passenger floor is malfunctioning, it might be stuck in the "cold" position or not receiving the signal to open the hot air path. This is a common failure point in older vehicles.
* Blend Door Cable (If applicable): Some models use cables instead of actuators. A broken or frayed cable could prevent the blend door from properly positioning itself to allow hot air through.
* Vacuum Leak: The HVAC system in your Caravan likely uses vacuum to control the blend doors. A leak in the vacuum lines can cause the doors to not operate correctly. This is less likely than a faulty actuator but worth considering.
* Low Coolant: If your coolant level is low, the heater core may not be getting enough hot coolant to heat the air properly. Check your coolant level and look for leaks.
* Clogged Heater Core: Although less likely to cause *only* cold air from the passenger floor, a partially clogged heater core could restrict hot air flow, potentially leading to insufficient heat in that specific vent.
* Faulty Temperature Control Module (TCM): The TCM is the electronic component responsible for receiving your temperature selections and relaying the signal to the actuators. A faulty TCM could send incorrect signals, resulting in cold air.
Troubleshooting Steps:
1. Check Coolant Level: The easiest thing to check first. Low coolant means your heater won't work efficiently.
2. Listen Carefully: With the heater on, listen near the passenger side dash. You might hear clicking or grinding sounds indicative of a failing actuator.
3. Manual Blend Door Test (Advanced): If you're comfortable with some automotive work, you might be able to manually manipulate the blend door (after accessing it). This will tell you if it's mechanically seized. However, this requires removing parts of the dash and should only be attempted if you have experience.
4. Vacuum Line Inspection (Advanced): Visually inspect the vacuum lines connected to the HVAC system for any cracks or disconnections.
Recommendation: The most likely solution is a faulty passenger-side blend door actuator. Replacing this part is a fairly common repair and often relatively inexpensive. You can find replacement actuators online or at an auto parts store. However, unless you have experience with automotive repairs, it's best to take your Caravan to a qualified mechanic for diagnosis and repair. They can accurately pinpoint the problem and fix it efficiently.
