Flying Spur AC only acts weird with rear passengers, front seats totally fine

[cody sutton]

Bit of an odd situation and hoping someone here has dealt with something similar before I book an appointment. my Flying Spur has this thing where the AC is perfect up front, cold air, no complaints from me or whoever's driving, but whenever I've got people in the back the rear vents just don't seem to keep up the same way, starts cold enough but kind of tapers off after fifteen or twenty minutes into a longer drive. my wife noticed it first actually, she was in the back on a longer trip we took a few weeks ago and mentioned it felt like the air just got progressively less cold the longer we drove, even though upfront I hadn't noticed anything different at all. at first I honestly wondered if it was just her being more sensitive to temperature than usual, but then a friend sat back there on a separate occasion and said basically the exact same thing without me even mentioning it beforehand, so clearly there's something actually going on rather than just one person's perception. did some reading last night trying to understand if this is a common thing with these dual zone rear setups, and came across This AC repair garage for Bentley cars in Sharjah that talked specifically about rear climate systems sometimes tapering off during longer drives due to either a struggling rear blower or occasionally a rear specific refrigerant issue separate from the front system entirely, which actually made a lot of sense given how the front has been completely unaffected this whole time. still not fully sure if this is something urgent since it doesn't happen on shorter drives at all, only becomes noticeable after a decent stretch of driving with people actually sitting back there, but with a few longer family trips coming up soon I'd rather get this sorted before it becomes a bigger annoyance mid drive somewhere far from home. has anyone dealt with rear only cooling issues like this on a car with a separate rear climate zone, curious whether it ended up being something related to the blower specifically or a completely separate issue that only affects the rear side of the system visit here https://caracrepairsharjah.ae/brands/bentley .