AC Issues – Warm Air on Passenger Side + Hissing Noise

[RWP]

Hi all,

Hoping someone might have some insight into a persistent AC issue I’ve been dealing with.

My AC has been looked at by a couple of garages and re-gassed twice this summer. After each regas, both sides blow cold air as expected. But after a couple of weeks, the problem returns: the passenger side (RHD) starts blowing warm/hot air, while the driver’s side stays cold-ish.

One garage mentioned the system “holds pressure for longer than is usually tested,” which makes pinpointing a leak tricky. When the issue reappears, I hear a very noticeable hissing noise from inside the dash - but only when the AC is turned on. This noise isn’t present immediately after a regass. I have a video, which I'll try to attach.

I’ve tried resetting the AC distribution doors countless times and even removed the interior panels around the centre console to inspect the actuators. From what I can see, they seem to be moving correctly.

It’s becoming a bit of a mystery, so if anyone has experienced something similar or has suggestions on what to check next, I’d really appreciate it!

Thank you

2018 1.4 Leon FR Technology

 

[cairus]

Replace expansion valve

 

[DaveS]

If the regas resolves it temporarily then there is a leak. No amount of messing with the flaps is going to change that. The hissing might be the gas boiling in the heat exchanger as it gets low.

 

[SuperV8]

One garage mentioned the system “holds pressure for longer than is usually tested,” which makes pinpointing a leak tricky. When the issue reappears, I hear a very noticeable hissing noise from inside the dash - but only when the AC is turned on. This noise isn’t present immediately after a regass. I have a video, which I'll try to attach.

When they say 'holds pressure' what they probably mean is it hold a vacuum - as the machine will pull a vacuum and wait something like 10 mins to check for leaks.
This isn't the best - as it really should be tested under pressure to check for leaks - as the AC systems works under pressure. This is done by pressurising the system with nitrogen - but takes longer so is seldom done.

This hissing you hear is a sign it is low on gas - so you have a leak. They also should add dye so you can check where the leak is.

 

[RWP]

Thanks everyone for the responses!

I have service coming up so I think I'll have them replace expansion valve (can't be too costly?!) and re-test for leaks.