I have an 06 Dodge Dakota with a peculiar AC issue that I need some help narrowing down.
-AC always works on start, gets cold, and blows at set speeds
-After about 15 minutes, if it is hot and humid outside, condensation builds on the ducts.
-At highway speeds after about 30 minutes, the duct by the drain tube freezes (see picture). Ductowrk behind dash sweats.
-Once the freezing begins, the air output gradually slows down, but stays cold. Air blows at lowest setting even when set on high, however when the speed is set to high you can hear it sounding like it wants to blow harder, but no additional air comes out. I am assuming the freezing is blocking the path of air.
-NOT A DRAIN TUBE ISSUE. The drain tube has been cleaned multiple times.
-When the car is off, the drain tub dumps an incredible amount of water compared to what I have seen on other cars.
It might not be a bad idea to have the gauges connected and see what’s going on with the low/high side pressures.
Sometimes with the loss of a little refrigerant the low side can get a little abnormally low. If the low side pressure at elevated RPMs is hovering around and below say 30 PSI the evaporator can freeze up. The rough rule of thumb is that the low side pressure is equivalent to the evaporator temperature.
Another potential cause is a low pressure switch not cycling the compressor off often enough. I’ve seen a few switches that were actually adjustable. Not being familiar with the Dakota I have no idea on that particular model.
Something to consider if it’s not an air flow issue.
The signal from the evaporator temperature sensor is monitored to prevent freezing, the PCM cycles the compressor clutch accordingly.
At this point switch off the compressor but leave the fan on, the ice should melt and airflow restored. If the compressor won’t disengage, the relay or clutch may be stuck.
I did just try a recharge kit. The pressure readings were interesting as they fluctuated throughout the test. I noticed that the compressor runs almost constantly at idle, and when it does the pressure dips from 35 to 25psi, then when the compressor kicks OFF briefly the pressure spikes up to 40, then ticks back down to 25 and repeats the cycle. No matter how much refrigerant I put in, the pressure readings did not change.
