I am pretty sure a new compressor will come with the correct amount of oil
Mac.

 

It's not a new compressor but a known-good used one unfortunately.

 

A rough rule of thumb is half for the compressor, a quarter for the condenser and a quarter for everything else. The amount of oil is not super critical unless you put too much in. If you think the 'new' compressor is pretty empty then, if it were me, I would put half the total amount in and cross my fingers.

BTW if you think the old compressor shed debris into the system then fitting an in-line filter to the inlet of the new one is a reasonable idea.

 

Thanks John. Never heard of an inline filter for AC, but it does make total sense. Any clue where I could source one from? I'm DIY so don't have the ability to make up custom hoses.

 

There’s two specs of R134a and Pag oil depending on whether you have the thick or thin condenser. You should have a sticker on the top of your n/s wing under the bonnet detailing the amount of refrigerant. Otherwise, The Bentley manual lists both and a guide on identifying which you need.

Interestingly, the R134a refill bottles sold at Halfords have almost the exact correct ratio of refrigerant to Pag oil (within ~0.5% if my maths was correct). If refilling yourself, remember to alternate between holding the bottle horizontal and vertical nozzle down to make sure you get a good mix of oil to refrigerant.

 

Thanks Alex, interesting info. I was avoiding filling myself as I thought it was tricky to do so from empty just through the low pressure port. Plus, it’s probably no cheaper to get it done by someone like QuikFit than it is to buy a several cans from Halfords.

 

Best find an AC specialist, not QuikFit or Halfords. Just Google a "air conditioning specialist near me"
Mac.

 

I’ve been reading around this a bit recently and it does seem a bit marginal DIY. My shed told me it could be £60 or twice that depending on the vehicle. Got the impression my 08 would be the cheaper end. Really impressed on the TT. I wonder if the even smaller cabin of the soft-tops are even more efficient?

 

Yup, if DIYing you’ll need to buy a good vacuum pump and a set of manifold gauges so you can run a leak-down test. Shed needed one and a quarter cans of R134a and Pag oil combined.

The outlay was around £200 so will take a few recharges to pay for itself.

 

Hello, As a recently retired refrigeration and A/C engineer there will be certain criteria you will need to follow to ensure a good result. To this end it might be better if we could communicate by email? I apologise if I am breaking any Forum rules! My email address is bobthomas911@outlook.com.
As a starter you will need to ensure you have a clean system, usually we used Nitrogen to blast through any rubbish and old oil from the system. Do NOT pressurise the system as the condensers are manufactured from thin wall material and are rated up to a certain psi/bar pressure. If you can get a cyclinder of Nitrogen get the fitting and pressure hose line too. You won't need a gauge as you will only be pushing through the Nitrogen in order to elinimate old oil/non condensibles etc...
The system can be blown through to eliminate MOST of the old oil as the new breed of oils LOVE moisture, and you do NOT want moisture in the system.
Remove the old drier, get a new one the same size. Do not open the end seals until just before installing the drier. When you blow through the system remove the drier before connecting the line from the Nitrogen to the system.
REPLACE the old oil in the second hand compressor. There should be an ID plate on the compressor body that will inform you of the amount of oil that should be in the compressor body. Charge amounts are not hyper critical but if you follow that info you won't go far wrong.
Use good quality spanners when undoing the ends of the lines, if you can get hold of refrigeration flare spanners, so much the better.
I think by now you can see the length of the replies I can send you!!!
If you wish to persue this then just email me.
Cheers for now!

 

Hello, As a recently retired refrigeration and A/C engineer there will be certain criteria you will need to follow to ensure a good result. To this end it might be better if we could communicate by email? I apologise if I am breaking any Forum rules! My email address is bobthomas911@outlook.com.
As a starter you will need to ensure you have a clean system, usually we used Nitrogen to blast through any rubbish and old oil from the system. Do NOT pressurise the system as the condensers are manufactured from thin wall material and are rated up to a certain psi/bar pressure. If you can get a cyclinder of Nitrogen get the fitting and pressure hose line too. You won't need a gauge as you will only be pushing through the Nitrogen in order to elinimate old oil/non condensibles etc...
The system can be blown through to eliminate MOST of the old oil as the new breed of oils LOVE moisture, and you do NOT want moisture in the system.
Remove the old drier, get a new one the same size. Do not open the end seals until just before installing the drier. When you blow through the system remove the drier before connecting the line from the Nitrogen to the system.
REPLACE the old oil in the second hand compressor. There should be an ID plate on the compressor body that will inform you of the amount of oil that should be in the compressor body. Charge amounts are not hyper critical but if you follow that info you won't go far wrong.
Use good quality spanners when undoing the ends of the lines, if you can get hold of refrigeration flare spanners, so much the better.
I think by now you can see the length of the replies I can send you!!!
If you wish to persue this then just email me.
Cheers for now!

Good advice, that entire post 💪😎

 

Just an addition to my previous reply and this concerns the use of refrigerants. Considering 134a will evaporate at about -25deg ish, you DON'T want any contact with your skin as "freeze burns" are quite painful. Several years ago there were several "laws" passed in order to regulate the use of refrigerants and eventually became "F-Gas regulations" which to put in a single sentence requires a qualified person that holds an F-Gas cert to "handle" refrigerants. So, beware as the "powers that be" show little patience to those who infringe on these regs. I went for a course... £400 please, an exam etc etc to get mine... I use mine as target practise with some arrows when I'm a little...mellow... shall we say. I'm amazed anybody can obtain 134a on the open market, but there it is... My near final bit of advise is to fit the compressor and then leave the rest for a A/C engineer to purge the system, replace the drier, leak test and then vacuum the system. (One has to be careful when putting the system under a vacuum as it is possible for some air to be drawn in through the compressor shaft as it was designed to stop and leakage of oil to the atmosphere. As an aside it will always be best practice to turn on the A/C every four weeks (max) in order to maintain an oil seal on the output shaft. You do this as an oil molecule is larger than a 134a refrigerant molecule, so try not to let the shaft seal "dry out".) So, once the system is not leaking and the integrity is good then one can charge the system. One does NOT charge the system with liquid, unless you want the compressor to seize. 134a is not a nice refrigerant and does not take prisoners... In fact, all refrigerants need to be respected. I've seen 500hp compressors internally destroyed due to a thing called "liquid slugging" pure refrigerant going through the compressor, and as we all know you can't (really) compress a liquid. OK, sorry if this turned out to be a version of the Gettysburg Address for A/C systems. Take care out there!!!

 

^^^^^^^^^^ I’ll forget most of this but AC on once a month and every month will be mentally filed away. Thanks.
When a shed does the job rather than a specialist; what shortcuts can they get away with? Drier replacement for example?

 

^^^^^^^^^^ I’ll forget most of this but AC on once a month and every month will be mentally filed away. Thanks.

Just leave the A/C on, there is no point turning it off.

Best way to keep A/C working properly is to use it.

 

Any shed should have an F-Gas certificate, the fines for a commercial establishment breaking these regs are severe. What would the price difference be between a shed and a specialist? Yes, a specialist will charge a bit extra but it may be worth it in the future, lowered stress levels and the knowledge that the job has been done by a person who does it all the time. Hence the job could well be completed a bit quicker than a garage, AND the A/C chap may well do all the work outside your home so you know how long they have been working on your car.
Hope this helps!!

 

Haha I reckon you are only semi-retired. Anyways I’m in deepest Cornwall and we don’t have specialists because of the population density. ( One of the hits when I googled specialist air conditioning is a well known local rogue. He tried to get me to spend a grand for his services ( clutch bearing) when the local main dealer charged me £799) as you can see I’m still outraged

 

Hmmmm, thought I replied but then I had to sign in and now I think I lost it... Try Simon at RK Engineering in St Agnes. Don't know how far they are away from you but it's worth a try. Mention my name (Bob Thomas in Colyton, Devon). Simon is giving me advise on my competition TT. If he doesn't do this ask if he knows who can.

 

Thanks, always up for a roam over the north coast cornish roads. I’m out most days for a pleasure drive and that’s just twenty miles away.

 

One thing I’ve always been interested in “hacking” - the aircon won’t run below 5C ambient temp, which has always felt a little high to me as misting and condensation in cold weather are a pain, especially in the winter months here in the UK.

Is there a way - eg through coding, or adjusting the resistance of the outside air temp sensor - to have the aircon engage as low as eg 1C ambient?

 

One thing I’ve always been interested in “hacking” - the aircon won’t run below 5C ambient temp, which has always felt a little high to me as misting and condensation in cold weather are a pain, especially in the winter months here in the UK. Is there a way - eg through coding, or adjusting the resistance of the outside air temp sensor - to have the aircon engage as low as eg 1C ambient?

Find the air sensor and if you can put in a SLIGHTLY warmer position, you will only need a warmer position of 5 deg? I wouldn't start to change the resistance it should be easier to place the sensor in a different position.

 

Thanks all for the replies, particularly @Marshal man. Apologies for not responding sooner but like thousands of others, this weekend was largely spent stood in a field watching bands.

One final question for the experts. I am pretty much ready to bolt in the "new" compressor and condenser and dryer, with the plan to get the system leak tested and regassed shortly after. The TT AC system has a total PAG oil capacity of 135g but with a newly drained compressor and new condenser/dryer, how much should I put in? Will the rest of the system still have a residual amount. Was thinking about 70g into the compressor. Also, when the system is vacuumed out and refilled, will they put more oil in with the R134a? Really don't want it to be overfilled as I understand that's worse than not having enough.

 

Hello!! With regards to the amount of oil required. In my experience when I've fitted compressors I've never added or removed oil from the system, when I know the nature of the original compressor failure. If I had any suspicion that there may be a larger amount of residue oil I would blow the system through with Nitrogen. During this process I would place rags over the open ends of the system (do not pressure the system too much, but if you need to, go to 150psi) in order to prevent everything in a 2 mtr radius being spotted with oil. Believe me, it's bloody messy!!!! Now if this is done you will have a fair idea of the amount of oil that was in the system. Once you have ascertained the approximate amount of oil that's been blown out you could, if you really want to, remove an amount of oil.
But again, I've never taken oil out of a new compressor, but if pushed I would remove about an egg cup full from the new compressor.
Yes, to have too much oil will knacker the compressor, depends on how much there is in the system that shouldn't be there...
One COULD put more oil into a working system by a specialist but to be honest an engineer would only do that if he/she had a strong reason to do so.
I hope this answers your question!!
I would like to add at this point that if anybody needs to remove an A/C compressor, if the unit does not have fitted any shut off valves then the system will certainly require the refrigerant reclaimed. To do this "by the book" the engineer will need an F Gas certificate, and if the refrigerant is not going to be reused, a waste certificate, and this will be required with any reclaimed oil. It is the ENGINEERS responsibility to ensure they are properly qualified, not you, or anybody else!! The only time the Environment Agency gets jumpy is when anybody just cracks open any joints in the system. Please PLEASE DO NOT DO THIS! Refrigerant burns at a -30deg onto open skin is nasty, everything will be covered in oil, you don't want oil or refrigerant in your eyes, refrigerant liquid will blind you. As I've said before, it's nasty stuff.
Hope all this helps!! Any questions just ask, I have the time this week as I have COVID and I am self isolating, it's a real joy...

 

As an addition to all the other items that have been discussed, this morning I trolled through Amazon for a decent set of gauges that can be used for car A/C.
OK, so there is a set called LATINARIC Diagnostic Manifold Gauge Kit. Now these can come with either 3' or 5' gauge lines. For a pound more I would certainly recommend the longer lines, you don't want to arse around trying to place the set of gauges on some vibrating engine part when you can hook it onto the bonnet catch...
So these gauges record temp and pressure for BOTH sides of the system. Really, you only want to get involved with the Low side initially. The gauges come with adaptors to fit Audi but I would check, just to make sure.
Cost? Try £34.99.
These would be idieal for the home DIY'er as you would be kicking the gauges around for years, I think they come with a case too.
So that's my recommendation. Any questions please ask!!!

 

Just to add to this with an answer to the oil question, I had mine professionally done today, drained, vacuumed, pressure test etc etc and the amount of oil that was refilled into the system was 10ml as per the printout below. My gas was low and my oil was zero…..no leaks fortunately, and system refilled with 525g of R134A and 10ml of oil.

This was on a mk2 btw….