Ok, my father-in-law has an '03with 4.7 and dual A/C.

Yesterday i noticed his coolant was very low, so i filled it up via the filler neck and also added more to his resivour. Today he calls and says his A/C is blowing hot. I asked if his compressor his working, and if it is just his front, rear, or both A/C systems causing the problems. His compressor is working, and its affecting both his front and rear systems. He says with the A/c turned on its warm, with it turned off and just the fan moving its blowing hot. My thoughts are since i added coolant, his heater is working again, and the a/c is still working, but has a fault in the blend door or the actuator itself. Any other ideas?

Unfortunately i am diagnosing this over phone / texts and cannot see first hand the vehicle.

 

if you wanted to rule that out you could have him see if the a/c is cold after the engine has had time to cool off.

 

It sounds like he has the heat slider in the red..

I've done this before, accidentally. If the slider is in red, that's of course heat, and the AC will cool it off some (which explains warm vs hot).

How much coolant did you put in? I'm talking like how many cans.
It's hard to tell without you seeing the D in person.

 

I have an '02 model 4.7, 2wd without the dual system, and encountered many issues myself that i've always trouble shooted myself and fixed. So i was trying to show him some of the things i had done to mine. While i had his hood open, i just naturally popped his resivour open and saw it was bone dry. So i then opened the cap and saw very little coolant. Had him start the engine and saw no fluid movement. I started adding water slowly and had several air bubbles come out (added about 0.5 gallons). After i had some movement now and expanding to overflow the top, i replaced the cap and added water to th resivour.

After that i actually washed out his engine bay from buildup of dirt, dust, grime, leaves and everything else you can immagine! He drove home (about 60 miles) without a problem. Then today he calls and explains his a/c is not working. He did verify that the compressor is turning, and both front and rear vents are blowing warm air. He said when he turns off the a/c and just runs the fan it blows out hot. He also said both coolant lines from the compressor are hot (1 very hot, 1 warm).

My first thought is that his coolant being low, it wasnt circulating through the heater core. Thus the a/c wasnt having to compete. Adding the coolant now allows it to circulate through, now competing against the a/c system. This would mean the blend actuator is malfunctioning in some way.

Now the second idea is this is happening to both front and rear a/c systems, so maybe it is an air temp sensor maybe? (I'm not all that familiar with a/c systems, especially the dual systems)

He says they sliders are all the way to cold... really wish i could see the truck right now to verify some common sense possibilities...

 

since you say that both lines are hot or warm it sounds like a problem with the refrigerant or the compressor. One line should be hot and one should be cold. If both are warm the system isn't cooling to begin with so it shouldn't have anything to do with the heater core.

 

If you've charged it, then it's the compressor. If not, charge it and see where it goes, but thatguy is right here.