QuestionI have a 2003 Expedition and the AC had always seemed to work great. However on a recent trip it started acting funny. The AC was working properly until we got on the highway and cruised for a while (happened twice, on the way to our destination and home). The air continued to blow but didn't seem to blow as hard or cold as normal. No matter how low I dropped the auto temperature controls it had no change. The Expedition has rear AC controls and the air out of the rear vents was blowing normal and cold. I thought it was low on coolant so I bought a can of R134 with a gauge and when I hooked it up the reading was right at the normal to high level. I didn't fill it up and went out later to check it and when I started it up it was blowing hard and cold. Any ideas what it might be and how to fix? Thanks.
AnswerBob,
Let me get this right, while your front was blowing not so cold, and not so hard, the rear was blowing great, right? And the force of the air from the front was diminished. What this leads me to believe is that your evaporator is freezing up. This would both put a hindrance on the air flowing through it into the cab, and it would not be blowing as cold, because with it having a lower amount of air flow through it, it is unable to absorb as much heat.
How it works: The low pressure of the refrigerant inside the evaporator causes it to get very cold. As the air from the cab flow through the fins on the evaporator, the heat and humidity inside the air stick to the evaporator. The heat gets absorbed into the refrigerant and pulled through the system and let out at your condensor. The humidity usually condenses on the fins, and flows out through the drain on the bottom of your car. (This is why you see puddles of water under cars while their A/C is on) What I believe is happening is your low pressure inside your front evaporator is way too low causing your evaporator to get way too cold. The humidity, instead of rolling off and out, now freezes and slowly begins turning your evap. into a giant ice cube. Air does not flow through Ice, so your air flow gets diminished. And as I said, with less air flowing through it, it is not getting the opportunity to absorb as much heat, so your cooling effect is diminished. The reason your rear works fine is because it has a separate evap for the front and back. Now... your excessively low pressure is being caused by a restriction in your refrigerant line coming into it. Being that your rear is working fine, that narrows it down to being inside the front evap. line. The only thing separating this from the rest of the system is your orifice tube.
I recommend you having your front orifice tube changed, and I have no doubts you will see this issue go away. It is fairly easy to access (I have a 1999 expedition), but it will need to be done by a shop, unless you are certified and have the equipment, because the refrigerant will need to be recovered prior to opening the lines. While you are changing this, I also recommend you change your receiver/drier. It is even easier to access, and may save you from having to pay the shop fee for recovering and charging the system again later down the road. For a job like this I would be surprised if the shop quoted you much more than about 200 bucks. UNLESS the evaporator is much more difficult to access than the 1999 model.
I hope I was able to help a little. Thank you for the question and good luck in everything. If you need more assistance in the future, do not hesitate to ask.
