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.

 

[RWP]

Just a follow up on this.

My compressor and high pressure pipe were replaced... Not sure if just the pipe would have resolved my issue, but garage had already replaced the compressor before raising the pipe issue.

I was desperate with a newborn imminent and impending 36 degree heatwave.

So far it's working for last 3 weeks... Fingers crossed it holds up. It was not cheap!

 

[RUM4MO]

There does seem to be a lot of this "always replace the Hi side pipe when needing to replace the compressor as the flexible section will probably have started to become more porous than when new", the Lo side pipework where it has a flexible section must surely also be starting to get "too" porous back typically usually under a lower system pressure than the Hi side.

 

[RWP]

There does seem to be a lot of this "always replace the Hi side pipe when needing to replace the compressor as the flexible section will probably have started to become more porous than when new", the Lo side pipework where it has a flexible section must surely also be starting to get "too" porous back typically usually under a lower system pressure than the Hi side.

Ah OK, thank you, that does make sense!