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I have a 2009 model and the air conditioner is blowing hot air, the compressor is running and i can put my hand on the low pressure freon line under the bonnet just in front of the passenger seat and the line is very cold. This indicates that the AC system itself is operating well but there must be a flapper valve (or something similar) in the air ducting that direct airflow either over the AC coil or over the heater coil. Seems like my car isn't changing the air flow to go over the AC coil. Is it a fuse, a control unit, the devise that actuates the valve? i am at a loss where to even start looking. can anyone here help with some troubleshooting?
 

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The first thing I would do is make sure the thermistor that senses the temperature in the evaporator box is plugged in. Sometimes the connector gets knocked loose. I would disconnect and then reconnect the connector. It is located in the passenger footwell just to the center of the flat hidden shelf. I would also try moving the temperature selector up and down as well as turning the rotary knob with the blower on to make sure that air is being directed to all of the right places. I would also make sure that the front fan is coming on when the A/C compressor is engaged. If none of this works, you will probably need to have the HVAC system scanned to see if the controller is functioning as it should.
 

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You can get a freon recharge kit (not actual freon but the eco-friendly alternative they use now) at Walmart, Target, any major auto store and "juice up" your system.

usually around $30

I've done it to my 2008 twice (every few years)

Usually solves the problem.
 

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again, compressor is running, return line is very cold. system appears to be doing its job but there is hot air coming out of the vents, looks like an airflow issue, not a Freon issue
 

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Be careful not to overcharge you AC. If too much R34 is put into the system, the pressure can go very high, triggering the blow-off valve and venting coolant to the atmosphere. If the pressure is just shy of venting, it can put excessive strain on the compressor causing failure.

If your a do-it-yourself type, I would recommend purchasing a manifold gauge set to set to avoid damage.

Just my 2 cents
 

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Sometimes the early cars lost the desired temperature setting. Work the temperature lever up and down a few times and see if it starts cooling.

You are correct that if the suction line is cold the system is full of refrigerant. That means the hvac control unit either thinks you want a warmer temperature or an internal air door or its actuator went stupid. I suspect the former. Costs nothing to try. If working the temperature lever corrects the problem then it is confirmed. The only permanent fix is to replace the hvac control unit.
 
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