Any air con specialists on here

[jamesmark]

I have an old(ish) 4x4 that when the air con rolled out of the factory/was last working has an old R12 systems.

 

It has been sat for 3 years before I inherited it, even when the wife's grandfather was alive he probably never used the air con, he had the car since almost new in 1990.

 

What is needed to covert it to current R134a? I see kits which just comprise of only fitments & oil, what about condenser etc etc.

[rider]

You can do simple things to get the a/c up and running again but rather than R134a which is itself being phased out you may as well consider jumping to its replacement R1234yf which has a lower global warming potential. From an R12 system the differences will be the service ports; R12 ports are different to R134a which in turn are subtly different to the new R1234yf systems. So you will need new ports or port adapters. You can get R12 to R134a port adaptors, you probably can't get R12 to R1234yf port adaptors as R12 was phased out a long time agao now. So the first question is do you want to change the service ports, if not R134a it is but bear in mind R134a is currently on its way out and the price of that refrigerant reflects its dwindling status and it'll only get more expensive.

 

With either R134a or R1234yf they both need an oil change on the compressor as R12 used mineral oil and the newer refrigernats use synthetic PAG oils. The reason being the newer gasses don't mix (as in they are not soluble) with mineral oil. So, you need to solvent flush your entire system by pumping a solvent around the pipework to wash out all the mineral oil. You then need to change the compressor oil to a PAG oil. The PAG oil for R134a is not the same PAG oil for R1234yf because the R134a PAG's have only limited solubility in the new refrigerant.

 

Once you change or have adaptors for the ports, have solvent flushed the system and added in new oil then you only need change the drier and you are good to go with adding the new refrigerant. The AC will then work, not as well as the original R12 gas did because the system was designed for R12 and all the 3 refrigerants used have different pressure and volatility characteristics. They are all selected to be similar, but they are not the same. The newer gasses can be more porous through R12 system hoses than R12 was, so you may need to top us the system every three years instead of every 6 as before.

 

So its not that hard to do, you can even get away with not doing a solvent flush if you change out the compressor oil two, preferably three times to remove as much of the original mineral oil as possible. To do this though youd need to recover the refrigerant each time or just vent and replace (which is naughty).

 

So first up

Change the low pressure service port or buy an adaptor to fit the couplings for whichever gas you choose.

 

Second up

Buy PAG compressor oil that is specifically suited to the compressor and refrigerant. The compressor manufacturers stick with the same designs and the design determines what viscosity oil you need. So if it was ISO 100 for the R12 compressor, chances are high it'll be at or close to ISO 100 for the newer gasses. Il is more than enough for any compressor as they usually take about 300g. Replace the oil in the compressor. Whatever comes out goes in, the rest of the original fill charge will be distributed around the system. If you have solvent flushed the system then go for a full initial charge volume of fresh oil.

 

Third up

buy the gas (you can buy small quantities service kits as a private individual, you need a licence to buy the larger gas cylinder quantities

Or employ a refrigerant engineer to do it for you.

 

Fourth up

Change the system drier to one designed for whichever refrigerant you choose. This is located on or near to the condenser.

 

Fifth up

Buy a refrigerant pressure gauge set to couple your gas to the service port and through which you can meter the new gas into the system. You will want around 2bar pressure on the low pressure inlet port with the compressor running.

 

 

It probably reads more daunting than it actually is.

[jamesmark]

Cheers for that great info there, very much appreciated. It does not sound daunting, as I will source a company to do it for me, I do not trust myself with anything DIY.

 

My concerns will be needing to get condenser rebuilt due to lack of use. Hoses at first glance all look ok when I was looking for the hi & low valves, I may get lucky as the 4x4 has been garaged all it's life and has only covered just over 40k miles.

[rider]

If you get a proper fridge guy the first thing he will do is pull a vac on the system to check the integrity and pull out any residual R12. If it holds the vac you then know all components are good.

 

The hard part will be tracking down someone happy to work on a R12 setup. They may well find it too daunting if they aren't old enough to have worked on one in the past. The retrofit proceedure I outlined hasn't really been mainstream practice for around 20 years, so its going to be largely forgotten to never known unless you come across someone who has been doing the job for 30 years or more and has experiience with what was termed in the day - R12 to 134a retrofit. If you mention retrofit and they go whats that then move on.

[jamesmark]

If you get a proper fridge guy the first thing he will do is pull a vac on the system to check the integrity and pull out any residual R12. If it holds the vac you then know all components are good.

 

The hard part will be tracking down someone happy to work on a R12 setup. They may well find it too daunting if they aren't old enough to have worked on one in the past. The retrofit proceedure I outlined hasn't really been mainstream practice for around 20 years, so its going to be largely forgotten to never known unless you come across someone who has been doing the job for 30 years or more and has experiience with what was termed in the day - R12 to 134a retrofit. If you mention retrofit and they go whats that then move on.

 

Found a company out in Pickering that I phoned today, as noticed they done a direct R12 replacement using RS24, but that too has been phased out.

 

He does the complete conversion to R134a, takes out anything left by vacuum and then a leak test before any work is even started.

 

Happy path, all in to r134a comes in at £134. If I need any pipes done etc then will be more. I will need to ask him as forgot, if he does conversion to r1234yf.

[rider]

Thats a good price especially if its VAT inclusive. I'd just want to confirm before you go ahead what it includes and ensure at minimum its a mineral to PAG oil change for the compressor (preferably after a solvent flush of the evaporator, condensor and pipework), a new drier and a charge of R134a.