Have a 2009 T&C that recently starting having A/C issues.

Just completed a couple of 14 hour trips for vacation, and determined that the A/C is blowing cold when first going, but stops and eventually starts blowing warm air. If the system is shut off for a bit of time, it will start over again fine.

Here is my guess to what is going on:

There is a device/box that is responsible for controlling where the air is sent (defrost/front/feet) that is not working correctly and maybe stuck, causing ice to form and block the system. Once the ice melts after turning the system off for a bit, the cold air is free to flow as normal until the blockage happens again.

I did feel some cold water (condensation?) at my passenger feet when the system was shut off and recycled.

1) Could this be related to a clogged drain pipe?

2) Does it sound more like an issue with the HVAC controller and/or servo motors that control it?

Thanks in advance for the help!

 

The Evaporator Temperature Sensor controls freeze up conditions. This sensor may need to be replaced.

The A/C system is designed to provide the passenger compartment with low temperature and low humidity air. The A/C evaporator, located in the HVAC housing is cooled to temperatures near the freezing point. As warm damp air passes over the fins of the A/C evaporator, the air transfers its heat to the refrigerant in the evaporator coils and the moisture in the air condenses on the evaporator fins. During periods of high heat and humidity, an A/C system will be more effective in the Recirculation mode (max-A/C). With the system in the Recirculation mode, only air from the passenger compartment passes through the A/C evaporator. As the passenger compartment air dehumidifies, the A/C system performance levels rise.

Humidity has an important bearing on the temperature of the air delivered to the interior of the vehicle. It is important to understand the effect that humidity has on the performance of the A/C system. When humidity is high, the A/C evaporator has to perform a double duty. It must lower the air temperature, and it must lower the temperature of the moisture in the air that condenses on the evaporator fins. Condensing the moisture in the air transfers heat energy into the evaporator fins and coils. This reduces the amount of heat the A/C evaporator can absorb from the air. High humidity greatly reduces the ability of the A/C evaporator to lower the temperature of the air.

However, evaporator capacity used to reduce the amount of moisture in the air is not wasted. Wringing some of the moisture out of the air entering the vehicle adds to the comfort of the passengers. Although, an owner may expect too much from their A/C system on humid days. A performance test is the best way to determine whether the system is performing up to design standards. This test also provides valuable clues as to the possible cause of trouble with the A/C system.