Hi,

 

Looking for suggested diagnoses before I leave my car at a workshop...

 

On the 1st hot day where I would have liked to use the AC I discovered that the damn thing no longer works. No errors, the car behaves as if all is well, but if anything the air coming out of the vents is warmer than it is with the AC off. The only tentative difference I notice is that the instantaneous fuel consumption  doesn't increase when the engine is idling and I put the IC on forced cooling (temp. under 18 deg C).

 

My workshop tech suggested that I had the system recharged as a 1st check, as I hadn't ever done that since buying the car in 2013 (and I don't know if it had been done by the previous owner). I had that done yesterday, and asked they verify if the accessory belt (replaced this winter because it slipped and squeaked) was driving the compressor as it should. Turns out the AC fluid was only 1/5ths empty (no leaks detected) and the belt was installed correctly (so that's 90€ down the drain for nothing >:-( ). None of the fuses that seem relevant to me are blown either.

 

So what could this be? Another known-to-fail thing you discover when it fails for you and makes you redefine the concept of a "reliable car"...?

Are you able to scan the car with VCDS? I would imagine there would be a fault code stored for the pressure switch if the refrigerant level has fallen too low for the system to operate. My car is a 2010 model with 135,000 miles and I don't believe the A/C has ever been recharged, it still works fairly well although I'm going to have it recharged this year

I'd have to take it in to read any fault codes, I don't have the equipment myself. As I said, the level had fallen only by about 1/5th; they purged about 440ml and restored about 570ml, off the top of my hat. Unless there should be much more coolant in the system, but in that case their system (a Bosch unit) must be out of order or misconfigured.

 

The pressure switch reinitialises itself once the level is back to normal, I hope?

I had issues with the AC and the first thing I did was to take it for a recharge. KwikFit have a policy, that if with the recharge they cannot improve your temperature, they refund you the money - £60. 

 

During the refill they realised that i have a faulty pressure switch. Booked it with a master technician and he fixed everything. 

 

So you can take it for a recharge there. This can fix it. Worst case scenario, it wont fix it, but they will be able to tell you what is wrong with the AC. That was my case. 

 

I hope it helps

 

 

1 hour ago, RJVB said:

I'd have to take it in to read any fault codes, I don't have the equipment myself. As I said, the level had fallen only by about 1/5th; they purged about 440ml and restored about 570ml, off the top of my hat. Unless there should be much more coolant in the system, but in that case their system (a Bosch unit) must be out of order or misconfigured.

 

The pressure switch reinitialises itself once the level is back to normal, I hope?

 

As far as I know, yes. In older cars which use an electromagnetic clutch to engage and disengage the compressor, if the pressure switch detects the refrigerant level is too low it will simply never engage the clutch. However the Octavia uses a variable displacement compressor, there is no clutch so the compressor is always engaged, but I think an electronically controlled valve inside dictates how much refrigerant flow there is. I'm not sure what happens when the pressure is too low, presumably the valve is never opened and the refrigerant will flow through a small bypass circuit or something.

 

Once the system has been recharged and the pressure is within correct limits it should just work.

Hmm, my observation that fuel consumption isn't worse with the AC on would suggest that the compressor isn't running - or else no refrigerant flow means the thing runs without a measurable additional load.

 

FWIW, I also see no effect on mileage when the programmed temperature is reached (and is easy to maintain). So I guess the thermostat could be faulty too?

 

Is any of these protected by a fuse that is not clearly labelled as AC-related? I'm a bit surprised btw. that even the 40A fuses are in the dashboard instead of the engine compartment!

 

Will just have to see if my local workshop will do the diagnostic for free if I don't promise I'll order the repair. I strongly doubt they'll give a refund on the refill, but I can bring up the idea of a commercial gesture. Our two cars are serviced there (but we're not exactly frequent clients nor their only ones).

VCDS will log a fault code for low high side refrigerant pressure and also display a corresponding compressor shut down code but at something like 3 bar absolute but the system will stop giving out cold air before that happens.

 

Last time I topped mine up it took very little gas for the high side pressure to rise to where it should be and for full cooling to be re-established.

 

I think they have to design the systems to run with the minimum of environmentally unfriendly gas

On one of the ac compressors fitted to mark 2 Octavias  have a thing where a nut on the shear plate loosens over time and needs gunning back up. It fixed  non working ac on our car a few years ago.

 

 

VW Audi Seat Skoda Air Conditioning Compressor Pump Clutch Hub Plate Disc 5N0820803, 5N0820803A, 5N0820803E, 5K0820803A Repair Fix Kit Instructions Install Guide The Problem It is a common fault on these air conditioning compressors for the bolt on the shear plate to loosen, causing the splines within the shear plate to wear leading to loss of air conditioning. These air conditioning compressor pumps all suffer the same common fault. The bolt which retains the shear plate (attached to the drive pulley) to the pump shaft loosens over time. If spotted early the bolt can be seen unwinding itself, eventually it loosens completely and is lost. The pulley will continue to spin with the engine causing the splines within the shear plate to strip. Once this happens the air conditioning pump will no longer function and produce cold air as the pully can no longer drive the pump. Previously the only solution was to replace the complete compressor at vast expense. We now provide just the shear plate and bolts so you can repair your compressor and restore the A/C at a fraction of the price. Symptoms of the fault Symptoms include; no cold air from the air con system and or excess noise from the air conditioning compressor. When the system all appears OK - topped up, no leaks, all seems OK via VCDS logs it is worthwhile inspecting the bolt on the shear plate as this is likely the fault. You should be able to observe the bolt protruding from the compressor (if not yet lost) and the screw not turning despite the pully turning. This is a clear indication that the bolt and shear plate are damaged. Our kit will remedy this. Vehicles affected and compatibility Our kit will repair these compressors with this fault: 5N0820803, 5N0820803A, 5N0820803E, 5K0820803A. Please check the part number on your compressor before ordering, we cannot confirm with 100% certainty from vehicle make / model. Will fit the Delphi compressor only. Some models affected: Seat: Leon, Altea. Skoda: Octavia, Fabia

Edited 11 June, 20205 yr by seriesdriver

That could be the problem, but how am I going to explain to check this here in France (I understand maybe half of the explanation myself 😕 ). A link to the repair kit product description might help.

 

One thing: does this wear also occur when your AC isn't running (just the regular heating or ventilation)? I don't know about the previous owner (who had the car for just under 100000km) but I tend to use the feature as little as possible.

 

We got away with just tightening the nut here is link to product if plate too far gone otherwise its a new compressor job 

 

https://x8r.co.uk/air-conditioning-a-c-delphi-compressor-5n0820803-audi-vw-seat-skoda-repair-kit

 

Note this fix is only for delphi compressors if you have different brand fitted (skoda fitted at least two different brands over time) if yours isnt delphi this isnt applicable. 

Edited 11 June, 20205 yr by seriesdriver
added information

RJB, you should be able to look down and see if the bolt is present and if its turning.

 

I am in the next departement from you and have VCDS and aircon vacuum down & recharge facilities & would be happy to look over your vehicle to gain more experience, being in your shoes and in the same geographic location is what made me invest in the equipment.

2 minutes ago, J.R. said:

being in your shoes and in the same geographic location is what made me invest in the equipment.

 

Being in my shoes in my location is no fun either ... sometimes size does matter

 

Anyway, thanks for the offer, let's work something out over PM! Please do tell where one should look for this bolt though, could be of interest to others too.

 

Fortunately the repair kit isn't expensive. BTW, is this part driven more or less directly by the accessory belt?!

Sounds like the dreaded N280 valve to me, seeing there are no fault codes, and the A/C still not working, mine went 3 years ago, new compressor and condenser.

 

If you do get to someone with VDCS, have a look at the compressor shut off code, if that is 0.0 and still warm then it is the N280 valve.

 

Hope this helps,

 

Trevor AKA Aston Bodger

Probably but not always, failure of the shear plate or pulley splines will also have the same result, VCDS shows a compresor load and RPM but its simply a calculated figure.

 

My Yeti showed no fault codes, no shut off codes, showed high side pressure above the fault code point but was not cooling, put guages on and I could see it did not have enough refrigerant, low side dropped but high side barely increased, a small amount of gas had it functioning as it should.

 

I did have N280 problems on the Octavia though with exactly the same symptoms.

With mine it was ok on the shut off code was 0.0 which shown it was working, but as far as getting cold nope, pressures were ok too, I don't think it moved hence why I suspected the N280 valve.

 

 

 

Trev

If the pressures were OK corrected for ambient temperature, low side falling high side rising much higher then the N280 will have been functioning, if they both remained equal and unchanged either the pump is not turning or the N280 is not functioning.

 

Can those things be read from the printout made by the recharging system?

Well, that was (is!) frustrating...  My local workshop doesn't even want to look things over because they don't have the AC-specific tools, and at their workshop in the next town (where they did the refill) the guy at the counter told me "I don't know how to repair parts" and that they'll only install new components. I'd already put the place in that category (= hardly better than places like Speedy) but I still felt like slamming the door when leaving.

 

Same guy also claimed that the pulley is "débrayable", i.e. has some kind of clutch that lets the compressor engage only when you turn on the AC (just like what you find on alternators, according to him). While the principle makes a lot of sense it seems to contradict that I've understood from this thread, including observations like how the pulley splines will strip if the compressor seizes. Unless that only happens when you actually engage the AC.

 

At this point it becomes very relevant to ask if I run any risk by NOT getting the AC repaired. It's a tough decision because this is the bigger of our 2 cars which we use to go on holiday with, and those are about the only occasions where I actually use the AC (unless it somehow also helps with heating, in winter, even if you don't push the AC button). The repairs required if the AC pulley comes off on will probably be far more expensive than getting a new AC (and that's not even mentioning the risks if it happens on a crowded highway ... I've had an injector blow there...)

As far as I am aware the mk2 Octavia does not engage and disengage the A/C with an electromagnetic clutch like older vehicles, it uses a variable displacement compressor which is always engaged and the compressor power output is controlled by a valve inside the compressor which varies the refrigerant flow.

 

If you have climate control and you leave it in auto, you will find that the A/C is actually used year round. It's not just for cooling, it also dehumidifies the air which is very useful in winter when the humidity of the air is very low and the breath you exhale is extremely humid and condenses on the inside of the windows. The A/C helps keep that clear. It's also why the A/C turns on automatically when you use the front window demist button.

I'm still happy to check it over if you wish.

 

Pulley does not have a clutch, your feeling was right about the mécano.

 

Very little risk running it as it is, with low or no refrigerant it wont cause any wear because the oil will remain in the compressor, if the splines strip but the shear plates remain intact it will make a noise like the tinkle of breaking glass, especially when idling beside a wall or shopfront.

 

The pulley runs on a large bearing at the outside, the shear plates connect it to the inner hub & compressor shaft, if anything nasty happens then they will shear & the vehicle will drive as normal, most owners are unaware that they have sheared or the hib has stripped other than noticing the AC no longer cools.

I noticed that about dehumidification (but AFAIK I don't have a front window demist button).

 

Theoretically the AC should also be able to heat the car if it has an optional circuit that cools the engine (and then circulate air heated by its radiator back into the passenger compartment).

 

But it's as I thought, they guy at the workshop counter doesn't know what he's talking about...

Just a precision, if the pump seizes then the shear plates will break isolating the drive, the aux belt then drives the alternator as usual & the aircon pulley becomes an idler pulley.

 

The splines on the hub will only strip if the central retaining nut comes loose or was not correctly torqued, if everything is tight they will handle more torque than the shear plates that are intended to fail as the weakest link.

23 minutes ago, J.R. said:

I'm still happy to check it over if you wish.

 

I know, it's appreciated :)

 

You're a bit too far to just hop over to have a looksee which is probably going to tell me that I'm in for a new compressor, so let me first see if there are no other workshops around here that do offer to repair components that can be repaired.

I'm placing a bet on the N280 Compressor regulating valve (solenoid) being dirty, clean or replace.

 

Why... because mine is and it's a job I can't do without costly gas handling.

 

According to Elsawin VW fitted a more 'robust' solenoid on later models to alleviate blockages from small particles.

 

Most likely a dealer will charge for a new compressor instead of just the valve.

 

These may be of interest:

 

 

 

 

 

You get the idea.

Edited 26 June, 20205 yr by MicMac

Thanks for those videos, do you also have a link (or 2 :)) for where to get the replacement valve (exact required model)?