Air con

[PDJ]

Ok so sometime between last summer and the warm weekend that we had last week (which could have been this years summer) I have lost the cold from the air con

It was blowing warm

So started ring around for a sensible price to sort it out one garage wanted £75per hour to look at it and around £100 to gas it if he cured the leak

So onwards to the tyre places that re gas air con and got down to around £75 for the re gas but no they don't do anything else other than tell me jokes one tyre co manager told be they pull a 5 to 6 bar vacuum on the system

So I have on order an Amazon manifold and gauge set I have a vac pump and a vac regulator

I tried to pull a vacuum on the system last night it pulls to -10"Hg ok then but will not hold it so there is a leak

Have a set of O rings so can change them if it is at a joint

I think it is the shaft seal on the vac pump as there was a bit of oily dust on the pump which I cleaned off last week and it has not returned

The pump from BMW is not cheap so if this is not serviceable it could well be staying non AC

At the moment the system is at zero pressure and the clutch does not engage on the AC button I think this is how it works the system needs to see a pressure before it spins the vac pump so will try and pressure it with air (I know not idea as I don't have any nitrogen to hand but I can vac the system before a re gas


Anyone have any other ideas to help find the problem

 

[j3nks79]

Stick it the garage for a nitrogen test.
It could be leaking from anywhere in the system. Condenser seals or pipes. Or even the compressor.

And the compressor won’t run without the correct amount of pressure in the system.

And the problem you can have just using air vac is it’s not as thin as nitrogen so hard to spot small leaks. You can also pull seals into gaps which then creates a vacuum so you think the system is air tight. So false reading

 

[Pondrew]

Chances are it is the neoprene seal on the drive end of the compressor. You shouldn't need to replace it.

Get the system vacced and charged; when it runs again it will usually reseal the leaking neoprene.

This is exactly why in EVERY car's owner's manual it will say to run the a/c periodically all year. The neoprene seal needs oil to seal it. If left to dry out it shrinks and lets refrigerant past.
It is also the main reason why so many cars need 're-gassing' every so often.
A refrigeration circuit is sealed. It doesn't lose gas unless there is a leak

 

[Pondrew]

And the problem you can have just using air vac is it’s not as thin as nitrogen so hard to spot small leaks.

The only reason for using (dry) Nitrogen is that it is dry. The number one enemy of a refrigeration circuit is moisture. That is the only reason why a vacuum is pulled; to boil away moisture at ambient temperature.

 

[j3nks79]

And the problem you can have just using air vac is it’s not as thin as nitrogen so hard to spot small leaks.

The only reason for using (dry) Nitrogen is that it is dry. The number one enemy of a refrigeration circuit is moisture. That is the only reason why a vacuum is pulled; to boil away moisture at ambient temperature.

So you’re saying when I run nitrogen through a car ac system to find a leak it just boils the moisture away?

 

[PDJ]

This is exactly why in EVERY car's owner's manual it will say to run the a/c periodically all year. The neoprene seal needs oil to seal it. If left to dry out it shrinks and lets refrigerant past.

This is very true it happens on NH3 industrial systems but NH3 stinks so you know you have a leak, I have change enough mechanical seals in my time, steam turbines leak on start up through the shaft seals until up to temp and pressure in the same way but a different type of sealing system.

 

[Pondrew]

So you’re saying when I run nitrogen through a car ac system to find a leak it just boils the moisture away?

No. The nitrogen is just to pressurise it. Nitrogen is used because it contains no moisture and is also inert, so doesn't react with anything.
Pulling a vacuum boils any moisture away and the pump then sucks it out as steam.
The idea of pulling a 'complete' vacuum, of 30" Mercury or 0 torr (although it is impossible to do in practice) is that under a complete vacuum there is nothing remaining....nothing. From a refrigeration perspective, the 'nothing' means no moisture. The tiniest amount of water vapour in a system can cause havoc.

They generally do have driers built into the system (usually as part of a receiver on the liquid outlet of the condenser). These are to pick up any remains of moisture that evacuation can't, or doesn't, remove.

 

[Pondrew]

This is very true it happens on NH3 industrial systems but NH3 stinks so you know you have a leak,

I am always amazed ammonia is still used in modern day refrigeration. It is horrible stuff. There MUST be better alternatives. I know it is an extremely good refrigerant but boy is it nasty!

 

[raymond.harper]

Halfords has a free leak test. https://www.halfords.com/motoring/engine-oils-and-fluids/air-con/free-air-con-check-694050.html

 

[j3nks79]

So you’re saying when I run nitrogen through a car ac system to find a leak it just boils the moisture away?

No. The nitrogen is just to pressurise it. Nitrogen is used because it contains no moisture and is also inert, so doesn't react with anything.
Pulling a vacuum boils any moisture away and the pump then sucks it out as steam.
The idea of pulling a 'complete' vacuum, of 30" Mercury or 0 torr (although it is impossible to do in practice) is that under a complete vacuum there is nothing remaining....nothing. From a refrigeration perspective, the 'nothing' means no moisture. The tiniest amount of water vapour in a system can cause havoc.

They generally do have driers built into the system (usually as part of a receiver on the liquid outlet of the condenser). These are to pick up any remains of moisture that evacuation can't, or doesn't, remove.

This is what the AC machine does before injection of the refrigerant anyway.
No vacuum and you can’t go ahead.
I use a nitrogen bottle to find leaks. You can either hear and feel with your hands around the system where the leak is coming from.
Or
If it only drops pressure after 30 mins or so I normally use a leak detector like big blue and spray it all over the pipes etc. This then bubbles up to show where it’s leaking.

 

[PDJ]

I am always amazed ammonia is still used in modern day refrigeration. It is horrible stuff. There MUST be better alternatives. I know it is an extremely good refrigerant but boy is it nasty!

Had the burns from it drying out the moisture around the face seal on a BA set when sorting out a NH3 liquid leak and all the other sweaty parts of the body looked like I had red socks on when I went for a shower at end of shift

 

[Pondrew]

This is what the AC machine does before injection of the refrigerant anyway.
No vacuum and you can’t go ahead.
I use a nitrogen bottle to find leaks. You can either hear and feel with your hands around the system where the leak is coming from.

These fancy 'all in one machines' have killed the car a/c trade for us.
I have seen a few in garages that include a nitrogen bottle. So literally turn it on, get a cup of tea and the car is done when you get back.

Thirty years ago I used to make quite a bit by going round all the local garages and dealerships 'mending' a/c on cars. Body repair shops were always the best, as everything was all new and not filthy when I got into the engine bay.
In those days cars used R22 which runs at pretty high pressures, then went over to R12. Both been banned for years now.
I even carried a full a/c hose kit, aluminium piping, benders, fittings and hydraulic crimpers. I could make up almost anything on site. Those days are long gone, thank God!

 

[STC_Zed]

What state is the condenser in?

I bought my wife a 330i touring last year and the A/C wasn’t working. I had it regassed cheaply but it started getting weak and wiry in a few days it was back to blowing warm air. A mobile guy came out and there was a decent leak in the condenser. This was changed for a Nissans jobbie which wasn’t actually too expensive from autodoc.

Unfortunately the gas escaped a few weeks later and it turned out the high pressure line was also leaking! On the E9x cars the high pressure line runs along the top of a chassis rail. As it passes the wheel arch there is a hole one side and a heat shield on the other. Stones, mud and crap make their way through the hole and get trapped by the heat shield and the rot the pipe. It’s not easy to see either. I bought an OEnojpw for £161 and fitted it myself and the A/C guy refilled it for free and it’s been fine ever since.