A while back the aircon in our Fabia stopped blowing out cold air, and it's obvious from the engine note that the compressor is not kicking in when cold air is requested. A scan with VCDS threw up the code "00229 - Refrigerant Pressure 002 - Lower Limit Exceeded". I figure it's one of two problems: bad pressure sensor or leak in the refrigerant loop. My question then is whether there are any common issues that lead to this problem that I should be looking for?

 

As someone with little to no experience playing with aircon systems, I'm tempted to just hand this over to a mechanic but I'd like to have some sense of what the problem might be first, or whether it's straightforward DIY job.

VCDS will let you look at what it thinks the gas pressure is, it might just be short of charge and need recharged, or it might have suffered stone damage to the condenser, or worse the evaporator.

 

Do you have mobile car AC systems operators near you, one of them might be your best chance to get it diagnosed and recharged, or even repaired.

Go into measuring blocks under the Heating & AC controller in VCDS & it will show you the pressure in the high side of the system, if it has some then a recharge will probably get it up & running, if none then there will have been a leak.

 

Beware, I think that VCDS shows absolute & not guage pressure (hopefully someone will confirm) so 1bar would be zero pressure. - Confirmed by Rosstech link.

 

I have just been out checking mine, seems like the slow leak I had has healed up or I screwed up on the initial charge and the 2 subseqent recharges.

 

Buying an AC manifold test set (£30ish) is a good investment and will tell you a lot of whats going on internally, VCDS will tell you lots of whats going on extarnally, temperatures, flap positions, shut off codes, PWM current delivered to N280 modulating valve etc, with both you have the full picture, some study needed regarding high & low side pressures, ambient temps etc.

 

https://forums.ross-tech.com/showthread.php?633-Tis%92-the-HVAC-Season

 

 

Edited 4 July, 20205 yr by J.R.

Thanks for the suggestions. I'll take a look after I've done the front ARB bushes on the Superb - not looking forward to having to drop the front subframe to get at them.

Aircon systems are protected often by a dual pressure switch, to high - no worky......to low (leak) - no worky...ie compressor will not engage system will not function

 

kwik fit will recharge your aircon and if it does not lower the temp there is no fee.

 

On the flip side if you get it done and it stops again in a while, then you know you have a leak and it would need a dye adding and / or pressure testing with Nitrogen unless the leak is obvious, after a recharge a good leak is often able to be heard or seen by pipe joints etc, if you can hear it then its a start of where to begin to fix it.

 

What will probably happen is you get it charged then about a week or maybe a little longer it will stop again due to a leak "somewhere.

 

Fxing aircon leaks can be troublesome, BUT "imo" to even start fault finding you need to attempt to fully vac / charge the system first.

Edited 4 July, 20205 yr by UrbanPanzer

It'll be a pressure sensor giving a continuum of pressure readings. In contrast to  @J.R.'s comment about VCDS/G65 sensor showing pressure readings as absolute pressures, my experience with VCDS Lite is contrary. Zero indicated is atmospheric. I actually asked Dr Peter in the Ross-Tech forum if he could check his info about this, as it appeared to be based on a mis-reading of some published VW info, but got no response. (Post #38 in here). Possibly VCDS Lite and VCDS full do this differently, but I'd be surprised.

Edited 4 July, 20205 yr by Wino

Groupon recently had a voucher for ATS to do a regas, for £39.

Got my wife's 2015 Polo recharged by ATS today, I considered removing the charging port dust caps in case they got lost or not put back on - then thought I should really trust them to do the proper job, wrong now I see the low side dust cover has gone, so I'll need to buy a new one, why can't people do the job they are paid to do!

 

I checked the system over for leaks while working hard, by using a pumped sniffer, no leaks evident, at least I have recorded what I should have done years ago, ie taken a set of reading of ambient temperature, evaporator temperature, high side pressure and centre vent outlet temperature. Soon I'll check the running pressures using my fridge manifold as I should have done last year!!

Can you explain how the pumped sniffer works & how you use it, leak detection is my next apprentissage.

 

Strangely mine leak, if there was one seems to have healed up after 2 subsequent top ups when my first recharge dropped its pressure, I got into all sorts of problems doing the first one through overfilling using the cylinder inverted, the pump hydraulicing, swiftly venting pressure & hence losing track of the weight charged. It then dropped pressure fairly quickly 1 I topped up twice using the guages as by then I had no idea of what weight was in the system.

 

Its possible that somewhere along the line some air got in, does air have a lower particle size (or is it molecular weight?) than the refrigerant and more likely to leak out of hoses seals etc than the refrigerant gas?

 

I know if I air test any plumbing I have done (dangerous, I get as much water in the system as I can first) that the test guage will gradually drop over 24 hours but a proper leak would lose the pressure much sooner, if I fill the system with water, purge the air, connect the guage and close the mains valve the pressure does not drop off, if it did there would be a water leak, could it be the same with air in an AC system?

First the "pumped sniffer" I bought a used AN134 Leak Detector, this is a device same as I had used at work for many years and so trust it.  It has a sensor inside the body that it passes sampled "air" across and has adjustable sensitivity.

 

They turn up on ebay from time to time, it has a long flexible (stiff but bendable) wand that you can get into places that you want to check.

 

As no doubt you know, when starting from a vacuum, the plan can be to "dump" refrigerant into a powered down system in liquid form to get enough in to allow the system to start running, then its back to turning the cylinder back onto its base and continue loading until the transferred weight is correct.

 

Lucky you having been brave enough to buy a cylinder, so far, as a DIYer, I have only bought a 2Kg "tin" of R134 and transferring that takes lot of time unless I'm up for heating up the "tin".  I was given a band heater to speed things up when adding refrigerant when I was working, though that was using a "crazy" or "specialised" low pressure refrigerant which was circulated using a rotary pump and kept in liquid phase by means of  nitrogen blanket!!  Which was a horrible way to do things and caused no end of compromises when it came to recovering all the refrigerant into recovery cylinders!

 

Air will have bigger "particle sizes" than R134A - when trying really hard to make a system as leak proof as possible, Helium is the gas of choice as it has "particle size" a lot smaller than most refrigerants - I think, so if a system tests good with Helium,  it is good!

 

The main problem with air will be "is it dry?" if not small beads of frost can end up choking any throttle points in a system, plus compressing air will not return it to a liquid, not at normal AC compressor pressures.

16 hours ago, rum4mo said:

Got my wife's 2015 Polo recharged by ATS today, I considered removing the charging port dust caps in case they got lost or not put back on - then thought I should really trust them to do the proper job, wrong now I see the low side dust cover has gone, so I'll need to buy a new one, why can't people do the job they are paid to do!

 

I would phone them up and complain of the attendants lack of attention to detail! If they can find it, get them to post it to you, if you are not local. After all, it was their mistake, not yours.

 

You are right there, but there is always the issue with  "he said he definitely fitted it" - these places are not quality, so at best only doing some bits of the job, I'd think that "the manager" is just the guy willing to face up you selected from whoever is free to talk, so in my world not worth chasing, I've learned my lesson, getting the car back with it missing was a worry prior to dropping the car off, but in the end I forgot to remove it.

5 hours ago, rum4mo said:

 

As no doubt you know, when starting from a vacuum, the plan can be to "dump" refrigerant into a powered down system in liquid form to get enough in to allow the system to start running, then its back to turning the cylinder back onto its base and continue loading until the transferred weight is correct.

I didn't know, I learn things the hard way, if all else fails RTFM etc!

5 hours ago, rum4mo said:

 

Lucky you having been brave enough to buy a cylinder, so far, as a DIYer, I have only bought a 2Kg "tin" of R134 and transferring that takes lot of time unless I'm up for heating up the "tin".

It was a big investment which I could not make today after losing all income but that makes me pleased I did it at the time as I wont be throwing money at the incompetent robbers here, £230 I think and despite my **** ups it has used suprisingly little although I reckon getting the last few kgs out will involve heating.

@J.R., I'm guessing that you "flush" your manifold set with virgin R134A always prior to connecting it to the system, that is allowed and not considered to be an intentional release of R134A.

Yes I do but its very difficult to tell when the air is expelled and its just the gas escaping, I probably waste a lot but on the positive side having my own personal hole in the ozone layer means I have no need of a tanning salon, not that I ever used one anyway.

A kind stranger from another forum gave me a lift to the UK today, when he arrived in his Volvo V70 he apologised that it was hot inside as the aircon had not been working for a long time, that can soon be remedied if you have 1/4 of an hour I said!!!

 

Got his A/C working so the journey was pleasant despite the heat, got dropped of at my house in Sussex so I can pick up my old Octavia2 and return to France with it to sell it, its been standing since March 16th.

 

A/C system no longer cooling, suspect all the gas has leaked out  😞, will check with VCDS tomorrow.

 

At least it started, I had disconnected the battery & it tested at 12.46 volts and 45% life remaining.

On 04/07/2020 at 23:11, Wino said:

It'll be a pressure sensor giving a continuum of pressure readings. In contrast to  @J.R.'s comment about VCDS/G65 sensor showing pressure readings as absolute pressures, my experience with VCDS Lite is contrary. Zero indicated is atmospheric.

This confused me on my son's Fabia 2. That had no A/C and the G65 VCDS reading was zero. Caused me to waste effort changing the sensor, control module and still getting a zero reading.  All the car needed was a re-gas and then the G65 reading was about 5.  The A/Cs been fine for couple of years since that re-gas.  So I can confirm no gas gives a zero VCDS G65 Reading.

1 hour ago, aubrey said:

This confused me on my son's Fabia 2. That had no A/C and the G65 VCDS reading was zero. Caused me to waste effort changing the sensor, control module and still getting a zero reading.  All the car needed was a re-gas and then the G65 reading was about 5.  The A/Cs been fine for couple of years since that re-gas.  So I can confirm no gas gives a zero VCDS G65 Reading.

 

I had that feeling but I was not 100% about reading zero when the system was extremely short of gas charge, so I did what maybe others would have done in that situation and quickly depressed the Lo side port valve core and was rewarded with a "too low" hiss!