Air-con re-gas

[Darrell]

How come we see in car ad's that the air con needs re-gassing. Isn't the system sealed like a pressurised heating ststem in a house?
Meaning that if it needs re-gassing there must be a leak somewhere?

Or am I totally wrong? or just confused?

 

[Will]

How come we see in car ad's that the air con needs re-gassing. Isn't the system sealed like a pressurised heating ststem in a house?
Meaning that if it needs re-gassing there must be a leak somewhere?

Or am I totally wrong? or just confused?

No, you are correct.

It's not a bad idea to have the system serviced once in a while I guess, but a need for 're-gassing' normally means a leaking system that is yet to be repaired.

Will

 

[ringway]

I would insist on any car I bought having a perfect working system.


I bought my W210 and the air-con wasn't up to scratch - "I'll just get it re-gassed" I said to myself.

It turned out to be the evaporator. £300 for the part and (if you are silly enough) £2000 for labour at a MB dealer. The dashboard has to be removed to access the evaporator.

 

[219]

Whilst it would be true to say 'there must be a leak' , it is normal for a small amount of gas to escape past the seals each year , with re-gassing being required periodically .

I suppose it is a little bit like having to add a small amount of air to your tyres from time to time without there neccessarily being a 'puncture' .

 

[Fredhead]

I would insist on any car I bought having a perfect working system.


I bought my W210 and the air-con wasn't up to scratch - "I'll just get it re-gassed" I said to myself.

It turned out to be the evaporator. £300 for the part and (if you are silly enough) £2000 for labour at a MB dealer. The dashboard has to be removed to access the evaporator.

Same with me. In my case it was the condensor and it cost about £350.00 with labour. Said condensor developed leaks twice thereafter, but replaced free of charge both times under warranty.

 

[Alan M]

Also I was told by someone in the industry very recently that a lot of car manufacturers do not fully fill the systems on brand new cars - they can cut costs by about 10%. The system will still work perfectly until it needs a re gas a few years down the line and unless there is a leak that is covered under warranty you will have to pay for it.

 

[lynall]

Whilst it would be true to say 'there must be a leak' , it is normal for a small amount of gas to escape past the seals each year , with re-gassing being required periodically .

I suppose it is a little bit like having to add a small amount of air to your tyres from time to time without there neccessarily being a 'puncture' .

That how i have always believed it to be, iirc as much as 10% loss per annum, nothing is ever perfectly sealed.



Lynall

 

[panason1c]

It's considered 'normal' for the ac system to need a top-up after 2 years or more due to seapage via the various seals, my ML lasted for 6 years before it needed a regas but bearing in mind there is also a certain amount of special lubricating oil mixed with the gas in the ac system (in the case of my ML, circa 190g) it isnt a bad idea to have a full drain and regas with fresh oil every 2 years anyway...............would you leave your engine oil for 2 years without changing it?............ac compressors aint cheap to replace!

 

[Dieselman]

There aren't any combustion processes to affect the oil in an A/C system though and the oil in the refrigerant isn't really running in moving bearings or gears, it just adds lubrication for the piston seals.

 

[gaz_l]

Seeing as you can get the air-con regassed for £50 at Kwik-fit it's a bit of a no-brainer to get it done if you're trying to sell the car (assuming you want to get top dollar for it).

If an advert said that the air-con needed re-gassing I'd guess that a) the owner was lazy about maintenance or b) they'd already tried that and the gas had leaked out overnight.

Either scenario points towards bills in the imminent future, and unless the car in question was seriously cheap I'd be off to look for another..

Cheers,

Gaz

 

[panason1c]

There aren't any combustion processes to affect the oil in an A/C system though and the oil in the refrigerant isn't really running in moving bearings or gears, it just adds lubrication for the piston seals.

The compressor is a component with many moving parts and the oil will degrade over time through heat, swarf, etc ...............no oil lasts indefinately.

 

[panason1c]

Air Conditioner Compressor Failures

LUBRICATION FAILURE
Just as this is a common cause of engine problems, so too is lubrication failure that most common cause of compressor problems. Remember, the compressor needs to be lubricated by a special refrigerant compatible oil. The oil is "carried" through the a/c system by the refrigerant. The oil will not circulate without refrigerant. Therefore, compressor failure due to a lubrication problem is caused by:

Loss of refrigerant which means no carrier of the oil and no lubrication for the compressor.
A blockage in the system. This will keep oil from returning to the compressor and will normally show up as too low a reading on the low pressure gauge. "Too Low" a reading means 0-10 PSI or a vacuum. The blockage may be in the form of:
A clogged filter drier/expansion valve/orifice tube.
Moisture in the system. (If the driver says the air conditioner works okay for a short time then starts blowing hot air and that if he turns it off for a while and then turns it on it works again for a short time, the odds are that there is moisture in the system. (A defective thermostat or clutch cycling switch will cause the same symptoms, however a watery smell will also be present.) Follow steps 1 thru 8 of the "SERVICE PROCEDURES" and make sure the drier/accumulator is replaced, and evacuate for 45 minutes.
A mechanically closed expansion valve. Some types may be removed and blown through (with mouth) to check.

 

[Dieselman]

The refrigerant isn't in the 'mechanical' side of the compressor though, just the compression pistons.

It doesn't lubricate the cam plate and bearings, for instance.

 

[panason1c]

The refrigerant isn't in the 'mechanical' side of the compressor though, just the compression pistons.

It doesn't lubricate the cam plate and bearings, for instance.

How, then, is the compressor shaft and associated cam surfaces lubricated?.....there isnt a 'sump' of any kind on a ac compressor and without lubrication the shaft would seize within a short period of time.........
A common area for refrigerent leaks apart from other areas is the compressor shaft seals.............the the gas/oil, has to be in the whole body of the compressor to ensure lubrication of all moving parts.

Edited.......

 

[Dieselman]

The refrigerant isn't intended to get into the mechanical side, otherwise it would take loads of refrigerant and eventually lock up due to hydraulicking.

Having only taken one compressor apart I can't say for sure but we just tipped a bit of compressor oil into the mechanical side to give it some lube.

Seemed to work OK for the next few years...

 

[panason1c]

Perhaps a AC engineer could post here to clarify?

 

[lynall]

I do a few a/c jobs on the trucks ar work and a few months ago took apart a failed a/c compressor for a look see, and the pag oil lubricates everything, pistons, gears wobble plate etc.


Lynall

 

[lynall]

Pics

 

[lynall]

More pics you can see the equivelant of the big end has let go and the rod and piston have jammed themselves into the side of the bore.
Lovely piece of engineering.

 

[IanT]

Thanks Lynall, that's the first time I've seen an aircon compressor in bits. Bet that one made a horrible tapping noise.

There are quite a lot of places the refrigerant can leak from - the least likely one I've heard of is apparently more common than I'd have thought - where the compressor is bolted together in more than one piece apparently sometimes corrosion starts between the parts of the aluminium and forces them apart slightly. Every air con leak bar one I've seen has been at a joint, the exception seemingly my old Mk4 Astra which had a tiny hole in the end of the condensor right next to the high pressure connection point.

I think MBs are more reliable because they run the compressor most of the time (not many owners run in EC mode?) and so all the seals are kept swollen by the gas / pag oil mix.

I bought a bottle of refrigerane and some manifolds for my own use, a friend has the full kit (and qualification to use it) should I need to open a system, but for adding some gas it's fine. Adding gas without first evacuating it and weighing in the correct quantity is at best risky, but with a conservative eye on the gauges it's quite possible to restore function.

Ian.