AC Light Flashing after Regas

[silversurfer10]

Hello everyone,

Recently, the AC on my CLS 219 would no longer blow cold air and when the AC was in operation I could hear a slight hissing sound. A few days after this, the AC light would flash whenever I turned the AC on.

I took the car to a garage and had the AC re-gassed. This seemed to resolve the issue - the AC would blow cold air, there was no hissing sound and the AC light would no longer flash. However, today, less than two weeks after the re-gas, I switched on the AC and the light was flashing again. I was wondering why this could be? Many thanks in advance.

 

[Petrol Pete]

At a guess ? All of the refrigerant has leaked out again , just because you did not hear it does not mean it has not gone . When the A/C service was done they should have conducted a leak test before re filling the system and then once re charged carry out a sniffer and UV lamp leak inspection.

Was this done ?

They might also have added a 'leak stop' product ...which worked for a short while . Take it to have the system pressure checked before committing to another 'service' . Let us know how you get on.

 

[OneForTheRoad]

This happened on my aged old 2008 CLS , it leaked while using the air con , pressure test at standing was passing ok, obviously the gas moves further up the system when in use , making the pressure test kinda inconclusive.

 

[E55BOF]

The hissing is characteristic of a system running when low on gas; if there is a leak, it will leak all the time, not just when the system is running. A real pro will test for a leak by pulling the system down to vacuum and seeing if it holds it.

OP, you have a leak; I'd expect it would be the condenser. Have it diagnosed by a specialist, not a generalist garage, and take it from there.

 

[Gbrowncls55]

You will have a small leak from the condensor or one of the o rings in the piping, most likely the condensor. After a reagas it can take up to a month to lose the gas again from a small leak and its not enough to show up on the 20 min vacuum test. Very common.

 

[E55BOF]

The OP's car has lost its gas in less than two weeks.

 

[Phil1968]

Take it to a vehicle aircon specialist where they'll use nitrogen to properly pressure test the system. The machines your generic garage plug in, then walk away from, to let them "do their thing" doesn't do a pressure test, just a vacuum test that is the equivalent of -15 psi, when the system working pressure can be as much as 500 psi +

 

[Jobsworth]

A two week leak is going to be hard to find on a first visit unless the system has had some dye put into it on a previous visit. Hopefully the last engineer has added some dye and you might be able to find the leak now

 

[Gbrowncls55]

Even bigger leak then. But still probably get by the 20 min vacuum test

 

[OneForTheRoad]

Even bigger leak then. But still probably get by the 20 min vacuum test

I agree , and had first hand experience. Tested twice , by ats clowns . System 100 % ok and gave me my money back.

 

[markmifsud]

I had a leak but the local mechanics could not show a leak, it passed all vacuum tests. I located the leak by injecting some AC Dye into the system and putting some non CFC gas in to pressurise the system. The leak ended up being from the low pressure charge valve itself so whilst the vacuum test was being carried out it could not leak as the hoses were connected.

By using the dye and checking a week later with a UV Torch I found that the dye was showing in the charge valve. I dripped some soapy water into the valve and it gently bubbled.

Ordered a new valve from MB (£16), fitted, tested and recharged, problem solved.

 

[Petrol Pete]

I note when looking at AC servicing on you tube etc ( what a life I lead !!) all the decent service people replace the (schrader type) inserts in both the high and low side as a matter of course.. Makes sense to me .

 

[Gbrowncls55]

Just one other point. When I last had mine charged after replacing the condensor the a/c would not work until I cleared all fault codes even though there were'nt any! Aparently when the charge pressure gets too low when there is no gas, the pressure sensors cuts in to stop damage to the compressor by dissabling it. Although there is no fault code for this the "fault"needs to be cleared to restart the compressor. Although I doubt this is generally normal proceedure it has happened to me twice on two different MBs. So if you have recharged and it still doesnt work ( assuming you have no leaks) then try clearing all fault codes. ....worked for me.

 

[E55BOF]

Going back to the dawn of time and a 1994 R129, the aircon didn't work on that but there was still some pressure in the system, so I tried to top it up with a bottle from Halfords to see if that helped. The compressor wouldn't engage to pull the gas in, and I only got it to work by bridging the pressure sensor. It worked; I had cold air again.

 

[Erfan]

On my W211 after a new a/c condenser and regas, the a/c light still flashed, with a/c inoperative. It needed to have an a/c reset or code clear before working again. Maybe this is a normal procedure as it happened to me and 2 of Gbrownscls55 cars. If you do end up needing a new condenser then consider a place that can clear the fault codes too?