Hi all my air-conditioning is not working well and I have some gas left over from a previous car to use up. Where is the low pressure point. I am having a thick afternoon and can't get wiki working. I have 2015 3.0 td v6 l405

Dont do it.

The remaining gas and oil needs to be removed so a very specific weight of refrigerant and lube can put in. The system should also be checked for leaks.
Local places like kwikfit offer a check and refill for £30, not worth risking IMHO. BMW i3 Electric Car
2012 Full Fat RR 4.4 TDV8 (now gone)
2006 VW Touareg 3.0 TDi V6

I agree. I was in NI last week and went to use the a/c in earnest and it was just not happening. went to our local ATS and they emptied, tested, cleaned and refilled my system in less than an hour.
They measure a specific amount of refrigerant back in to the system so I would not be happy interfering with it myself

Rob Now running a 2016 Autobiography plus a Bentley Continental GTC
Previously ran a Lincoln Navigator and 18 XC60 T5
Before that a pile of Jeeps, Mercedes and Jaguars and Porsches, Mustang and Volvo.

I really do doubt that trye outfits offer much in the way of a/c expertise.

I have done my own R134a or R1234yf top offs for over 30 years and its quick and easy. I could check and add refrigerant to my L405 sitting outside in maximum 10 minutes. The OBD even gives a pressure and evaporator temperature readout in real time. It'll tell you if the compressor clutch is engaged and you can see if its cycling or running as it should. I really doubt those tyre fitters are that plugged in.

On one car that I have owned for 25 years it does need a R134a top off every 6 years. Usually around 60 - 100g on a 660g charge. So it loses around 2% a year through hose porosity. 10 minutes every 6 years using about, at todays price, £5 of gas from service cans or £2 gas from larger cylinders. Little wonder the tyre fitters love topping off a/c systems.

My 2016 has the low pressure service port on the right side. Its a R1234yf fill system but I believe the 2015 is r134a. For anyone interested in servicing their own a/c system which does exclude total loss leaks then you can buy service cans (sub 1kg) of R134a without requiring a FGas certificate. For R1234yf no FGas is required. I have service cans and cylinders for both R134a and R1234yf ready to pull every 4 to 6 years at service time to top off the a/c system if required.

So how do you know how much is in the system, and how much to top off.....?? and BTW my 2014 is on R1234yf gas..  Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

You either fill on weight having evacuated the system and then add in the OEM recommended charge which from memory on the L405 is 1kg.

Or, if you don't have access to a vacuum pump that pulls the gas out into an empty cylinder and weigh scales then you see what is happening on the running pressures using the OBD data or using a port coupled gauge set.

The website linked below gives the pressure guide for different ambient conditions for R134a. R1234yf is similar. For my L405 it was 1050kpa target evaporator pressure from memory for the ambient temperature that day. My car a/c wasn't working when I bought the car, it was only managing 680kpa. That was good, a relief, as having any pressure said there was still refrigerant in the system so I wasn't facing a a/c ending leak. So I monitored the inlet pressure on a low port gauge and checked the evaporator pressure on a high port gauge and confirmed with OBD data. I added gas until the specified pressure for the ambient temperature was obtained for both compressor inlet and outlet pressures. Result was a working a/c in comfortably under 10 minutes.

https://www.rechargeac.com/how-to/ac-system-pressure-chart/

There is lots of information online in videos and in write ups on how to perform DIY top off service on a car system. The only thing I'd recommend people avoid is the so called drop in replacements which are hydrocarbon blends. Those will not mix in the same way with the compressor oil as the original refrigerant. They are a fraction of the price to produce so offer savings but the solubility of the gas in the oil is critical for the compressor lubrication as the gas is soluble in the oil thinning it down considerably and also the oil entering the system does need to return from the evaporator and condenser back to the compressor.

baz000000 wrote:

I really do doubt that trye outfits offer much in the way of a/c expertise.

Quote:

I have done my own R134a or R1234yf top offs for over 30 years and its quick and easy. I could check and add refrigerant to my L405 sitting outside in maximum 10 minutes. The OBD even gives a pressure and evaporator temperature readout in real time.

Quote:

It'll tell you if the compressor clutch is engaged and you can see if its cycling or running as it should. I really doubt those tyre fitters are that plugged in.

Quote:

On one car that I have owned for 25 years it does need a R134a top off every 6 years. Usually around 60 - 100g on a 660g charge. So it loses around 2% a year through hose porosity. 10 minutes every 6 years using about, at todays price, £5 of gas from service cans or £2 gas from larger cylinders. Little wonder the tyre fitters love topping off a/c systems.

Quote:

My 2016 has the low pressure service port on the right side. Its a R1234yf fill system but I believe the 2015 is r134a. For anyone interested in servicing their own a/c system which does exclude total loss leaks then you can buy service cans (sub 1kg) of R134a without requiring a FGas certificate. For R1234yf no FGas is required. I have service cans and cylinders for both R134a and R1234yf ready to pull every 4 to 6 years at service time to top off the a/c system if required.

Great info there Baz . Most helpful as my aircon has stopped blowing cold air, hoping it just needs topped up and not leaking SDV8

I, in a previous work life was directly involved in the transitions from CFC's to HFC's in the early 90's and visited just about every compressor manufacturer in the World at that time.

A bit of insight into some of the issues compressor manufacturers face with the gas and oil combo. The gas needs to be soluble in the oil as there is a lot of oil carried into and around the a/c system that must be returned back to the compressor otherwise it'd get oil starvation and die.

CFC molecular size is larger than the corresponding HFC so a bit of a problem with retrofit R12 to R134a systems was the R134a would pass through the rubber hoses at a much higher rate. The solution to this was to manufacture what were termed barrier hoses which are rubber hoses with a plastic insert. This greatly reduced the migration rate of gas out of the system and into the atmosphere but it never totally eliminated it.

Hose leakage has always been a factor in car a/c where fixed metal pipe coupling isn't possible due to flexing from a fixed condenser and a moving vibrating engine.

The refrigerant recovery equipment does do the work of evacuating, leak testing and refilling (on weight) a system. It doesn't need a highly skilled operative to work it. The machine does cost a bit of money though so for the DIY motorist it isn't a viable purchase but charging reading off pressures is a perfectly valid way to fill a system. It isn't high risk at all as that is how a refrigeration system works, pressurising the gas so it becomes a liquid that then evaporates to provide the cooling. Its no more risky than letting someone loose with an air hose to fill up their tyres. I have seen people confuse Bar for psi at Supermarkets and I wouldn't recommend that they go ahead and DIY their a/c system. Best to leave that to the tyre folk in that instance.

Here is a site that discusses flexible hose coupling porosity to refrigerant gas, quoting Du Pont data comparing barrier hose performance to non-barrier hoses. I doubt it'd concern any tyre fitters at all but it makes for interesting reading especially if you have an older 911.

https://griffiths.com/mr-ice-project/barrier-hose-upgrade/

baz000000 wrote:

I, in a previous work life was directly involved in the transitions from CFC's to HFC's in the early 90's and visited just about every compressor manufacturer in the World at that time.

Quote:

A bit of insight into some of the issues compressor manufacturers face with the gas and oil combo. The gas needs to be soluble in the oil as there is a lot of oil carried into and around the a/c system that must be returned back to the compressor otherwise it'd get oil starvation and die.

Quote:

CFC molecular size is larger than the corresponding HFC so a bit of a problem with retrofit R12 to R134a systems was the R134a would pass through the rubber hoses at a much higher rate. The solution to this was to manufacture what were termed barrier hoses which are rubber hoses with a plastic insert. This greatly reduced the migration rate of gas out of the system and into the atmosphere but it never totally eliminated it.

Quote:

Hose leakage has always been a factor in car a/c where fixed metal pipe coupling isn't possible due to flexing from a fixed condenser and a moving vibrating engine.

Quote:

The refrigerant recovery equipment does do the work of evacuating, leak testing and refilling (on weight) a system. It doesn't need a highly skilled operative to work it. The machine does cost a bit of money though so for the DIY motorist it isn't a viable purchase but charging reading off pressures is a perfectly valid way to fill a system.

Quote:

It isn't high risk at all as that is how a refrigeration system works, pressurising the gas so it becomes a liquid that then evaporates to provide the cooling. Its no more risky than letting someone loose with an air hose to fill up their tyres. I have seen people confuse Bar for psi at Supermarkets and I wouldn't recommend that they go ahead and DIY their a/c system. Best to leave that to the tyre folk in that instance.

baz000000 wrote:

Here is a site that discusses flexible hose coupling porosity to refrigerant gas, quoting Du Pont data comparing barrier hose performance to non-barrier hoses. I doubt it'd concern any tyre fitters at all but it makes for interesting reading especially if you have an older 911.

https://griffiths.com/mr-ice-project/barrier-hose-upgrade/

Quote:

We perhaps have to disagree here, how much oil remains in the system? what about adding oil? The real danger of over filling and I have seen one of these kits used where it was overfilled and it blew the side out of the compressor when it hydraulic locked. So not quite the same as an air hose.