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!

 

[RWP]

The hiss is back and warm air from passenger side again!

I've notified the garage... But not sure how much money I can keep putting into this!

 

[hippocoffee]

I have this same issue - warm air on passenger side, vaguely cool on driver side and hissing when the AC is turned on. Really noticeable in the recent hot weather.

I took it to a garage recently who took a look at it and said that it looks like there is a leak in the condenser (in one corner), so I'm getting that replaced in the next few months to see if it fixes the issue. I did re-gas the system 3 years ago but it didn't make much difference and just continued to get worse, so a leak seems likely in my system. If that doesn't fix mine I think I'll give up and forget about it because it seems a bit of a nightmare.

Have you been to a car air conditioning specialist? They might have more experience and know what to look for vs a general garage?

Hope you get it sorted!

 

[ArchNemeziz]

In this kind of situation where you have no clue where the leak is I really suggest to ask they refill it and add correct amount of UV die so it becomes apparent under a UV light where the leak is exactly.
It could be any of the piping/tubes with micro fractures. I had mine refilled just recently and it was more than 50% below the rated amount but they couldn't find the leak but there was aluminum piping of the pressurised AC system which had rubbed against an airflow plastic near the front wheel and slightly damaged the piping. Since the replacement is 300€ I opted for them to just add UV die so if it does become an issue again we know where the problem lies instead of randomly replacing components in the system.

The issue could be a maintenance valve or any piping which has worn over time. Repairshops often don't care if an expensive part needs to be changed since you're paying for it and the AC system can be an expensive problem. Refilling with die is the most non invasive thing you can do. Just make sure they know to add the right amount of die. The die doesn't hurt the system as long as the right amount is put in and can stay in there. Since you already had the service done make sure the shop didn't already add it since you shouldn't add a full dose of die again if it's already been added.

 

[nd-photo.nl]

Indeed, the piping is usually overlooked but I had to go back 3 times before I fixed the aircon issue on my girlfriends Opel Adam

1) Try to regas, leak somewhere
2) I found the condensor to be leaking, I swapped out the condensor. Try to regas, still leaking. They found a hose leaking on the crimped part of the hose when doing a pressure check on the aircon system
3) Replaced the combined aircon hoses (OE part, around 250 euro), try to regas: succes

And this is me doing the labor, it can become quite expensive real fast as replacing these items usually mean removing the bumper etc, making it labor intensive...

Estimated total cost; about 490 euros (again, with me doing labor, except for aircon filling part)

 

[ArchNemeziz]

And since it's a pressurised system you usually don't want to get a 3rd party part either.

 

[nd-photo.nl]

The car manufacturers won't make these lines themselves, but with these kind parts you will probably see a very low number of suppliers, one of which should be the OE supplier. Same with headlights, it's usually Valeo / TYC / etc

 

[RWP]

So, it's been in the garage for another week. Original works apparently still valid.

This time, 2/3 (I can't remember) O rings replaced, high pressure valve replaced and pipe re-seated due to possible pinch.

Those were identified with die as egress points.

Condenser apparently pretty battered but not leaking.

Fingers crossed for everyone with the AC Issues!

 

[RWP]

So, it's been in the garage for another week. Original works apparently still valid.

This time, 2/3 (I can't remember) O rings replaced, high pressure valve replaced and pipe re-seated due to possible pinch.

Those were identified with die as egress points.

Condenser apparently pretty battered but not leaking.

Fingers crossed for everyone with the AC Issues!

To add, the garage only charged me £26. It came back cleaned too.

It cost me more in an uber to go pick it up!