2007 Vue AC stays on in all floor modes

Have you confirmed it is actually blowing cold dehumidified air out the floor vents as opposed to unheated air coming out the vents at the floor? First situation points to the head unit likely being defective, second situation points towards restricted coolant flow through the heater core.

Don't quote me on either of these as I am not a Vue specialist.

Outside chance of the mode door actuator being hosed and hanging up during its intended movement. See if you can find a sequence of changing the mode that does not include the floor vents. Also listen to the dashboard to see if you hear a clicking noise. I have no idea where the mode activator is in a Saturn Vue. Let me know if you find

 

Yes I am referring to the control system in the dash.
Have you verified that the AC compressor clutch is in fact engaged all the time, or is cycling on and off all the time?

I'm not familiar with that control unit. Does it allow you to choose multiple outputs at once? For example windshield and lower footwell at the same time?

If the answer is yes, the system can only deliver AC air or non-ac air. Meaning I would expect selection of the windshield would override any other setting that would normally not be AC.

However, if you select only floor and dash and have not selected AC with the button, and the light is not on for AC, there should not be AC air coming out on the floor. Newer cars sometimes think they know better and will automatically engage or disengage AC, but I don't think they were doing that back then. Does this vehicle have an auto climate control or separate driver and passenger settings? Make sure they are both set to the same temperature when testing what's going on.

What year is this vehicle? I can point you to the circuit diagrams for the AC system. Is the AC button depressed and held in but not lit, or is the button out meaning disengaged but AC air comes out on the floor when it shouldn't? These are all troubleshooting steps and we can explore the possibilities on the circuit diagram. Usually it takes a lot of things to be in specific States for the lights like AC, defroster for the rear, etc to light up. They are usually one of the last things in the circuits so that if they are not on when they should be or they are on when they should not be, that is a big hint when analyzing the circuit diagram in comparison with what you see

 

Also, is recirculate on? Some cars turn that on by default when the engine starts even if you turned it off the last time you drove the vehicle

 

The one above at 12:00 is for the windshield and will be AC. It also has a down arrow which I assume means the floor vents. So cold air air conditioned air should be coming out the floor vents when the air conditioned air is blowing on the windshield. Seems to be intended functionality.

The rightmost working at 3:00 is obscured in the picture by the knob. Please take a picture of just that symbol so I can figure out what it means

 

Here is a link the HVAC wiring diagrams. There are actually three diagrams covering all of the different parts of the system. Probably best to print them out. It seems somewhat complicated, but all we are looking for is when is AC requested by the body control module or the ECM and how is the AC clutch relay closed meaning what signal leads to telling the relay to close also known as applying 5 volts across it.

The AC clutch physically cannot be made to meet with the compressor and drive the compressor without the voltage signal it needs to supply the current to the coils inside it. This means basically the relay for that must be closed or it ain't happening. I believe it is in the first diagram there is an AC control relay. I believe this to be the AC clutch relay but I only looked at it for 3 minutes so search around for other relays. The only thing I can think of off the top of my head is that that relay is defective and is staying closed some of the time when in fact it should be open. Like in those other settings. That is the easiest explanation. If that is not the case, then this gets very messy very quickly.

 

Yeah that'll happen. Apologies.

https://charm.li/Saturn/2007/VUE AW...trical Diagrams/Heating and Air Conditioning/

 

Bummer. Did you investigate the relay which I mentioned above? If the AC is on then that relay is closed, or there is another relay maybe somewhere between the fuse box and the ac clutch. Like I said above, the relay that controls the AC clutch has to close for the AC clutch to engage the compressor. No other way for it to happen. So I would determine which relay that is and there's nothing else to swap it out. Or if you understand relays, you can play with opening and closing it with a short wire at different terminals