A/C blows warmer in front than rear?

2017 CHEVROLET SUBURBAN
115,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC
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BIKENGEAR
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My A/C works perfectly in the rear of the vehicle. When below about 78 degrees the A/C works well front and rear, though the rear will be cooler. Turning off the rear A/C has no effect on the front temperature output.

Once the temperature passes 90 degrees, the front really struggles for 5 to 10 minutes of driving before it begins to blow cold enough to lower it.

I've checked the refrigerant and it was in the good zone, but it was only with one of those AC Pro refill kits, not a full set of gauges. Replaced cabin air filter.
Jul 28, 2023 at 11:10 AM
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STRAILER
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Yep, we need to know the high side pressure because you may have a compressor going out, this video will help show you how:

https://youtu.be/4EqdrBVb0sY

If the pressures are low on the high side and high on the low side the compressor is failing. If the pressures are good, can I ask if the AC performance on the front A/C system is the same for both sides, passenger and drivers' side? The reason I ask is I need to know if it is a blend door actuator problem. If the pressures are bad here is a generic guide to help you step by step with instructions in the diagrams below to show you how on your car:

https://www.2carpros.com/articles/replace-air-conditioner-compressor

and this guide may help as well:

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

You have either 134a or 1234yf refrigerant, do you know which kind your vehicle has? Check out the images (below). Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.
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Jul 29, 2023 at 1:28 PM
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BIKENGEAR
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Thanks. I have the wrong gauges for my R1234yf equipped car. I need to grab adaptors or a new set of gauges. All the air controls work fine. Left to right, defroster etc. I understand that there might be a leak, or my compressor might be going bad.

What I don't understand is how can the rear put out ice cold air while the front struggles to do the same?
Jul 31, 2023 at 11:40 AM
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STRAILER
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I would say it could be a blend door actuator, but the problem is on both sides of the front HVAC system?
Aug 1, 2023 at 9:53 AM
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BIKENGEAR
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Correct. Both sides in the front.
Aug 1, 2023 at 10:34 AM
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STRAILER
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Okay, can you turn the A/C system on full cold and then grasp the larger outgoing/low side tube coming out of the firewall to the compressor to see if it is cold? Also did you get those gauges to see what the pressure was? You may have an evaporator temperature sensor that is off, and it is telling the HVAC controller to adjust the temperature blend doors to warmer. We might want to do a CAN scan to see what comes up. You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

Check out the images (below). Please let us know how it goes.
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Aug 2, 2023 at 6:32 PM