w220 aircon failure :(

[glassdome]

I have a 1999 w220 (one of the early ones) s320. The car is only at 79000 miles and great, except my aircon is broken

I had it re-gassed but no effect.

Though this was carried out a national tyre centre.

The engine changes revs slightly when I turn the air con on so I think the pump is okay, I have also reset the system on the climate control, removal of battery and also reset of the fault codes through a DBMS reader.

I wondered if the gas pressure from national was insufficient for the compressor to kick in, as I have read on some posts that the w220 system needs higher pressure than normal?

Or could this be the compressor? Just for additional info having read other posts, the belt seems to be fine and the compressor turns. The revs shift when the compressor comes in. However, there is no cooling whatsoever. Just warn air and on a hot day it is unbearable.... luckily we're into winter soon

Any thoughts on what I could check would be great, or if the pressure aspect could be the issue?

Thanks in advance

 

[Doug1234]

Check the duo valves, they can stick not close off the hot coolant from engine

 

[Wighty]

A decent aircon repair guy or garage can inject a coloured dye into the system to spot a leak .

 

[joderest]

when they recharged the system did they say there was gas still in it, they should have done.
The new machines will not gas if it detects a leak.

 

[Doug1234]

If the compressors cutting in then its got enough gas to run

 

[Botus]

the condenser that sits in front of the coolant rad has a life.... the newer the car the shorter the life

I just had to put one on my 55k mile 221, if it was a Porsche you need them at 3 years and 20k miles because they more or less make them from tin foil, add 1/4 of a winters salt to the equation and its game over very quickly (not that mine ever got salt treatment)

mine still had gas in and still worked, but it leaked half out till the pressure was enough that the leak is mostly controlled, as the condenser wears the gas keeps leaking till it goes to low pressure

mine was running with 200g out of 1300g standard but that's with a variable compressor, the earlier ones with the big clunk and electromagnetic clutch cut out on low pressure quite easily

 

[mioba]

Normally after a regas they will work for a while until the gas is gone due to a leak. For it not to work immediately means a huge leak. Alternative there is some mechanical fault not letting it work at all. as mentioned check the duo valves.
Did the aircon place tell you it was low. by law they have measure what they out and then put back in based on specs.

 

[Paul1948]

Turn your temp setting fully down, if the temp still blows warm/hot you duo valve has failed....this happened to mine changed for £100 by my local Indy, looking at the unit after could have done it myself the faulty item is now fixed as the motors had seized, cleaned spindles and greased with silicone grease. Motors now work perfectly ready if it fails again. I was advised that the problem that the AC had been switched off. The same reason people have compressors that fail when not used in the winter months should always be run and just temperature changed this stops the bearings corroding and then seizing....good luck with the fault

 

[alexanderfoti]

If its your duo valve, grab one of the AC pipes on the right hand side with the valve cap on it. With the AC set to max cool, that pipe will be cold if the ac system is working, even if the interior evaporator is being overrun with hot air from a faulty duo valve.

 

[Botus]

on many car's, often the revs shift because the car is trying to compensate for the increased load the AC compressor should be bringing to the party, it doesn't have to mean the compressor actually cut in. Although on later cars they should have got the two joined up properly. Certainly on old kit like yours I wouldn't be surprised that

a) it compensates regardless of whether there's really a change in load
b) there's insufficient gas, when was it re gassed ? - if the leak is high it could drop down to low pressure inside a month easily
c) the condenser is leaking, get a torch and look round the edge of the condenser, you're looking for dark dusty patches rather than a clean aluminium colour, if it also looks a little oily in these places, its gone

 

[BillyBoy]

In the later W220s you could go into diagnostic mode by holding a couple of buttons, and could then scroll through to see temperatures, high and low pressure etc. I think the same is true in the earlier ones too. Just Google S Class Air Con diagnostic menu.

Also if you have one, shine a UV light around in the engine bay. Air con gas should have a UV dye added to help tracing leaks.

 

[Martyn Cannon]

My condenser is faulty on mine being replaced next week


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[glassdome]

Thanks all.

a bit more digging and info. When it was recharged by national the pressure held fine. However there was zero cold air, I’d even say it was a little warm. National agreed and so refunded me when I went back a couple of days later. When the refunded me they checked the system and I think they also extracted the gas to use for someone else.

I did hold the incoming and outgoing air con pipes when it had gas in and there was no noticeable coldness to the pipes. The revs did change but don’t know if the compressor actually kicked in or not.

I think I may have to bite the bullet and take it to a specialist. Trying to find a good indie is going to be interesting. If anyone has heard of or has experience with an indie called Huxleys in Fleet, Hampshire it’d be great to hear what they’re like.

 

[Botus]

not great they took the gas out, system health wise gas is good, using all the time is great...

all cars with AC get a sticker under the bonnet (often on the bonnet slam panel or rad fan cover) saying what gas type and how much the system should have. It varies on car size / quality / engine size and ambient conditions in the market the vehicle is built for.

in the UK roughly 600g on 1.6 hatchbacks, 900g on a 3 ltr and 1300g on a big boy motor.

the rules these days are

to extract gas and measure quantity (by seeing how much is there you already get a good idea of the health of the system) less than half the amount and its likely the leak is big enough they shouldn't refill.
then pull a vacuum and see if it hold for 10 minutes. if that's OK then you can refill with the amount on the label...

if it doesn't hold the vac they are not supposed to continue... but I can imagine 10 mins might drop to 2 or 3 and then they want some money so shove some in and take the money

 

[mattkh]

....... and how much the system should have.

Thanks for that. I will look for that value on the sticker. If it is not there, is there any other way of finding out how much
my car should hold?

Secondly, I have read somewhere that the aircon relay can be activated with a wire (and engine OFF) to hear the clutch on the compressor engage. Has anyone ever done that?

 

[Botus]

yes common idea, don't run it without gas !!!!

the handbook might say but could be different weight of gas on same type but different spec car

 

[davemercedes]

I was told (and subsequently read an article about AC longevity) that it should be kept on all the time because it is a system designed to condition the air/climate in the car. So I've followed that advice and never switch it off - I simply change the temperature setting to what I want during the forthcoming summer/year, My local guy checked and topped up the gas about 5 years ago and it does enough to keep me happy. However, I admit that it never feels quite cold enough in hot weather but I've learned to trust it to make it "comfortable" inside the car.

 

[pt-pro]

Have you found failure? Or still aircon doesn't work?