Driver Side/Passenger Side AC Differential

[NaOH_hurts]

I drive a 2017 Ford Fusion Hybrid SE, with dual climate controls. In October, I noticed the driver side AC was blowing very, very warm air despite being set to Max A/C. A calibrated thermometer was showing a delta of 19.2⁰ between the cold air on the passenger side (55⁰) and the air coming out of the driver side (74.2⁰). Looking through various forums, it looked like it might have been the driver side blend door actuator failing, so I went ahead and changed it. This did not help. A friend with a manifold let me borrow it, and I needed quite a bit of refrigerant, so I added it. Problem solved. The passenger side dropped from a 55⁰ to a 48⁰ and the driver side dropped down to a 51⁰.
Until now. The driver side is back to blowing warmer air. Not as bad as before, but about a 13⁰ differential when set on the max setting. My buddy with the pressure manifold moved, so I no longer have access to it, but I did check the low pressure AC line, and it was within range. Any ideas on what could be causing this? Did my new blend door actuator go bad perhaps?

[JohnHere]

Back in October, you measured a passenger side vent temperature of 55°F and a driver's side vent temp of ~72°F. You added refrigerant (no mention of how much), and for a while, the system performed fairly well—48°F on the passenger side and 51°F on the driver's side—still not adequate, IMHO. But now, it's producing warm air from the vents once again, particularly on the driver's side, which strongly suggests that the system has a refrigerant leak, not a blend-door problem.

A few questions, if I may:
—Have you had a professional A/C shop check it for leaks? If not, I suggest starting there.
—How many miles has this car logged, and how did you check the LP line? Also, does it have R-1234yf refrigerant?
—Is the vehicle located in this country, or is it offshore someplace? The reason I ask is because in most of the USA, it's generally too cold to work on the A/C system now unless you're in the Southwest or in the south of Florida.

[NaOH_hurts]

Thanks for the reply. To answer your questions in order:

-I have not taken it into a shop to check for leaks. Money is extremely tight at the moment. Luckily it's winter and I have some time to save a bit before I really need the AC. I added just under an 8 oz can of refrigerant in October.
-The car has 120,000 miles. I checked the low pressure line with a borrowed coworker's recharge hose and gauge (Sorry, links to outside businesses aren't allowed) and it is r1234yf. It has approximately 35 psi on the low pressure side (it was about 68⁰ outside).
-I am in Southwest Louisiana. It was 76⁰ today, but the cold front is on its way with a high of 46⁰ tomorrow, and estimated 5" of snow on Tuesday.

In your opinion, 48⁰ on the passenger side and 51⁰ on the driver side is not adequate, how low of a temp or close in temp should they be?

[JohnHere]

-I have not taken it into a shop to check for leaks. Money is extremely tight at the moment. Luckily it's winter and I have some time to save a bit before I really need the AC. I added just under an 8 oz can of refrigerant in October.

I hear you on the money issue. As for the 8-ounce can of refrigerant, the problem is that a Manifold Gauge Set (MGS) can't tell you how much refrigerant the system contains. The only way to determine how much R-1234yf was in the system at that time (or any other time) is to recover the refrigerant using a Recover/Recycle/Recharge (RRR) machine. Usually, only professional shops have them due to their high cost. The RRR machine automatically weighs the refrigerant that it recovers and reports that info to the technician on the machine's digital read-out. Chances are, it was low when you added refrigerant. How much, though, is anyone's guess. And you can't just blindly "top-up" a system with modern cars.

Look for a decal on the radiator support, under the bottom front-edge of the hood, or elsewhere in the engine bay that tells how much refrigerant and oil the system takes. Post that data.

From the information on the decal, you or a shop will be able to gauge how much the system contained and how much it would need to be recharged to. My guess is that the specification is about one pound net weight of refrigerant, or a little more. In any event, the amount needs to be exact for the system to run properly, and the refrigerant must be weighed-in to a well-held vacuum using an RRR machine or refrigerant scale. No other method of charging or recharging will work.

The car has 120,000 miles. I checked the low pressure line with a borrowed coworker's recharge hose and gauge (Sorry, links to outside businesses aren't allowed) and it is r1234yf. It has approximately 35 psi on the low pressure side (it was about 68⁰ outside).

Measurement of the low-side pressure using a single gauge like that doesn't tell us much. You'd need to post both low-side and high-side pressures using a MGS for the readings to be meaningful. Also, the gas engine should be set to a fast idle of about 1,800 RPM, the electric compressor (this is a hybrid vehicle) would have to be running, the temperature of the system set to Maximum Cooling, doors and windows open, and the blower set on Medium to maximize the heat load on the system. All of this should be done at an ambient temperature of 80°F or above. Only then can the pressures be recorded and the system performance evaluated.

I am in Southwest Louisiana. It was 76⁰ today, but the cold front is on its way with a high of 46⁰ tomorrow, and estimated 5" of snow on Tuesday.

Best to delay any A/C work until the ambient temperature reaches 80°F or above, as mentioned. For a properly operating system, you should be seeing about 40°F or so at the center dash vents at moderate vehicle speeds and at the stated ambient temperature.

[NaOH_hurts]

I sincerely appreciate your input and help.