Hey everyone! I have a 2007 STX special edition with the 5.4L 3V and here's the issue. Yesterday after fixing the A/C at my house ironically my truck started blowing warmer and warmer air while driving. Later in the evening on my home it was blowing cold air again.. Did the same tonight. Checked refrigerant with guages and it was spot on. Lines were hot and cold as they should be. Checked a/C clutch and no gap and kicks on and off as it should. I did notice that there is no water dripping under the truck from the A/C which isn't normal. Would this cause this issue or is it a result of something else and what would that be ?

 

I don't know much about the a/c system but I do know normal a/c units should at least drip water a little bit, no matter the temperature.

 

You can have sticking or broken blend doors. Maybe blend doors that switch from cold to hot are vacuum controlled and you have a vacuum leak.

 

When the A/C is working properly and if your not in the middle of the Sahara desert (your in FL) you generate condensation that normally drips onto the ground. That water is going somewhere or its filling the A/C plenum. Pull back the passengers carpet and see if it is wet with water trickling down the fire wall. Sounds like A/C drain is clogged. Have you heard any water sloshing from that area?
I am not sure a clogged drain is causing your issue but you need to make sure that drain is clear and functioning. Water on the floor boards gathers in the channel under the door trim piece and can cause electrical issues.

 

I spent lastnight pulling the wheel well and getting to the pipe stub they call the A/C drain and hooked up a small shop vac to it. Your right the AC should be producing water even for the short time that it's cold. I have vinyl floors so it would be easy to spot water, I didn't think to check the wire channel but i will today. After 5 minutes with a shopvac stuck to the drain line it still isnt dripping anything. Thats why I figured it be smart and get some suggestions before dropping big money on a new A/C system. Of all days I'm in Ga today and it's a cool 101 today.

 

I went back and checked the channel and it's dry as well. Still no water from the drain tube, or in the floor board or the channel. Still ice cold for the first 6 or 7 miles the. Gradually gets warmer all the way to wherever your headed and then once I cools then back to ice cold. Did have one new development my battery was dead and down to 10.8 amps. Could a dying battery cause this? It's a fairly new belt but if it's slipping then could that be the issue?

 

Update. I cut a flap in the plenum box behind the glove box and was able to get the wand of a bug Sprayer in there with some coil cleaner in it. Applied and rinsed 3X and that finally unclothed the drain hose. Used some mesh tape and water weld to seal it up. Finally after all the crap what it finally ended up being was a 3.99 diode located in the fuse box under the hood.

 

While there is a diode under the hood that is part of the A/C clutch circuit, it's HIGHLY improbable that it was the source of your original concern. It's only purpose is to prevent damage to other stuff when the clutch de-energizes. Other than that, it doesn't have anything else to do with how or when the system operates.

FWIW, some of your symptoms suggest evaporator icing but other symptoms that should have been also present weren't mentioned.

 

The water backing up could help freeze coil but usually it just causes water damage. The diode should only come into play when coil is released it shunts the back emf to ground to protect your system. Back emf is reverse polarity . It should not conduct when power is applied- only on release . If diode was bad you would blow fuses if its shorted out .
Your little compressor clutch relay can get burnt contacts and become flaky, its on drivers side fender . I replaced mine at a big box store generic one . Run your fan at full speed to keep coil from freezing on long trips , you can also use recirculate to stop drawing in hot air on bad days.
Running fan on low for too long can freeze coil it needs warm air to take the cold away , you may need to see if your recirculate vent control is working .
Not enough cooling is usually a sign of too low freon -r134a or whatever.