August 9, 2016

A/C freezing up?

This time of year I get quite a few reports of air conditioning systems blowing hot air, then after about 15 minutes working again.

Because of the hot humid conditions, 90% of the time this is caused by the a/c evaporator freezing up.  Your college student's refrigerator/freezer does the same thing but much slower.  Eventually they have to thaw out the freezer with a pan of water with the unit off.  The same thing happens in your car if there is not enough air flow over the evaporator.  It will freeze up.

Normally there are two reasons for this.

#1  The cabin air filter could be clogged with debris and needs to be changed.  This filter is much like the furnace filter in your home except much smaller.  There are lots of YouTube videos demonstrating how to change the filter on your model of vehicle.

#2  You are running the a/c on too low of fan speed for the weather conditions.  If the air is hot and very humid, a low fan speed may not be enough air flow for the air conditioner to keep up with the condensation, so the water stays too long in the evaporator and it freezes.  The best way to combat this is to run the fan on high and push the recirculate button.  Or if equipped, put it on the max/a/c setting.  This way, the high fan speed is pushing the water out of the evaporator, and the recirculate feature is only allowing the a/c to cool the already cool air in the car, rather than constantly taking moisture and heat out of outside air coming into the car.  Full blast makes it last.

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