Hi,

 

I'm using my mother's Fabia for a while and her aircon doesn't work. I want to fix it for her as a birthday present as we live in a very hot place.

 

When you press the a/c button, nothing happens. No dip in the revs and no compressor sound. Initially I did a scan with VCDS and it said the gas pressure was too low.

 

It's a 2004 1.4L 16V 100hp Comfort model

 

Control Module Part Number: 6Y0 820 045 

  Component and/or Version: Klimaanlage        X0840

           Software Coding: 

            Work Shop Code: 

2 Faults Found:

01596 - Motor for Outside/Recirculated Air Flap (V154)

        55-00 - Adaptation Not Successful

00819 - High Pressure Sensor (G65)

        07-00 - Signal too Low

 

I got a gas recharge. When I went back they said that the compressor is dead. They had removed the gas they added afterwards.

 

Another scan showed additional codes:

 

Control Module Part Number: 6Y0 820 045 

  Component and/or Version: Klimaanlage        X0840

           Software Coding: 

            Work Shop Code: 

3 Faults Found:

01596 - Motor for Outside/Recirculated Air Flap (V154)

        55-00 - Adaptation Not Successful

00819 - High Pressure Sensor (G65)

        07-00 - Signal too Low

00898 - Control Circuit A/C compressor

        30-10 - Open or Short to B+ - Intermittent

The same scan a few minutes later showed some additional ones, but I'm not sure they're relevant or affect the a/c issue:

 

Control Module Part Number: 6Y0 820 045 

  Component and/or Version: Klimaanlage        X0840

           Software Coding: 

            Work Shop Code: 

5 Faults Found:

01596 - Motor for Outside/Recirculated Air Flap (V154)

        41-10 - Blocked or No Voltage - Intermittent

01596 - Motor for Outside/Recirculated Air Flap (V154)

        10-00 - Adaptation Limit Not Reached

01596 - Motor for Outside/Recirculated Air Flap (V154)

        55-00 - Adaptation Not Successful

00819 - High Pressure Sensor (G65)

        07-00 - Signal too Low

00898 - Control Circuit A/C compressor

        30-10 - Open or Short to B+ - Intermittent

 

My main question is, does this mean that the compressor is dead, and will replacing it (and recharging the gas) fix the issue?

 

I'm happy to buy and install a compressor if it will fix it, but I don't want to sink hundreds of pounds into an old car and end up with nothing to show for the birthday present. This is my first forray into car a/c systems so any advice would be very welcome.  I don't know if the garage did a full diagnostic and arrived at their conclusion, if if they just put the gas in and assumed it was the compressor when it didn't turn on.

 

It looks like you can get second hand compressors on ebay for a decent price, £30-£50 or so. There are a couple of part numbers, 6Q0820803D and 6Q0820803J which both seem to fit. I tried to get the part number of the one fitted but I couldn't get access to see anything. Any light anyone can shed would be very much appreciated!

 

Thank you in advance

Could be as simple as a busted wire going to the solenoid valve on the compressor. Take off the engine undertray and locate a bracket with three or four connector pairs on it, on the front face of the gearbox. A/C is the brown connector pair. This would be consistent with the 00898 fault code, and would be a nice free fix if all you need to do is repair one or two wires.

Great, thank you. I will be back home in a week or so, and I'll give that a try. It will be great if that works. Is there any way to test it without taking to back to a garage and paying €40 for another diagnostic? I will do that if I need to. Or find a place that doesn't charge if they can't get it working.

 

If that's not the problem then I'm guessing that the dodgy connection is inside the compressor, and the unit needs replacing?

The compressor is mechanical, not electric.

If there are wires going inside then there must be some kind of electrics in there, no? Something to engage the clutch to get the compressor spinning with the belt. I wondered if that solenoid was not working, and so not engaging the compressor correctly.

12 minutes ago, aurumdeus said:

Great, thank you. I will be back home in a week or so, and I'll give that a try. It will be great if that works. Is there any way to test it without taking to back to a garage and paying €40 for another diagnostic? I will do that if I need to. Or find a place that doesn't charge if they can't get it working.

 

If that's not the problem then I'm guessing that the dodgy connection is inside the compressor, and the unit needs replacing?

If you find broken wire(s) I'd say it's extremely unlikely that there is another fault as well.

Ok, cool. Fingers crossed there's a broken wire then. If there are no issues with the wiring is the best bet to replace the compressor? As I said they're not expensive, the only hassle will be actually fitting the thing. Definitely do-abe though.

The solenoid valve varies the quantity of refrigerant pumped, which is continuously variable. There's no clutch on these.

1 minute ago, aurumdeus said:

Ok, cool. Fingers crossed there's a broken wire then. If there are no issues with the wiring is the best bet to replace the compressor? As I said they're not expensive, the only hassle will be actually fitting the thing. Definitely do-abe though.

The fault code says there's a wiring problem, in my opinion.

One other thing - look at the compressor pulley with engine running. Does the central nut turn with the pulley?

Ah ok, I understand. So the compressor is always turning with the belt, and the solenoid allows the refrigerant into the compressor when you turn the a/c on. This extra load is what causes the drop in revs. As I said, this is my first forray into car a/c systems. 

 

I'll give the wiring a good going over when I'm back and see what I can find. 

39 minutes ago, aurumdeus said:

Ah ok, I understand. So the compressor is always turning with the belt, and the solenoid allows the refrigerant into the compressor when you turn the a/c on. This extra load is what causes the drop in revs. As I said, this is my first forray into car a/c systems. 

 

I'll give the wiring a good going over when I'm back and see what I can find. 

 

Yes.

 

Like I said the compressor is mechanical and it's permanently engaged, I agree that it's likely to be a wiring issue.

The aircon compressor has a clutch which disconnects the compressor from the pulley under high engine load so you get full beans for the engine power road speed ...eg when you floor the throttle with the air con on...

 

Personally I would clear all codes, drive the car using the air con for a week & scan again see what codes turn up...

1 minute ago, fabdavrav said:

The aircon compressor has a clutch which disconnects the compressor from the pulley under high engine load so you get full beans for the engine power road speed ...eg when you floor the throttle with the air con on...

 

Personally I would clear all codes, drive the car using the air con for a week & scan again see what codes turn up...

 

No it doesn't.

 

It has a shear clutch which snaps if the compressor seizes so that your auxillary belt doesn't break. Other than that it's permanently engaged in bypass mode until you actuate the solenoid as Wino explained above.

 

I was under the impression from something I read when I got the car that it had a clutch which operated as per my post above..

 

That video is helpful...learn something new everyday....

It's quite possible that the HVAC module and engine ECU 'chat' to enable exactly the behaviour you suggest.  I don't know if it does happen, but a VCDS logging session might spot it (vaguest of feelings I may have tried this and not found it, but that could've easily been something else).  Full beans on the loud pedal could easily be communicated to the HVAC module and the PWM'ed A/C flow control backed off temporarily?  Possibly only implemented on the more performancy variants, so possibly not on either my Polo or the missus's 3-potter.

That video was very interesting, thank you Wino. 

 

One issue I can see is that the system is currently empty, so the pressure sensor will presumably prevent the solenoid moving even if I fix wiring or try to use VCDS for more codes. 

 

I guess I'll get home, lift the car up and see what I can find for wiring. Then I'll take it from there.

 

Would it be possible to pressurise the system with air from a compressor to overcome the low pressure sensor and get the system engaging, or could that potentially damage things?

Can your version of VCDS look at live data/measuring blocks?  If so you could watch the pressure sensor output to see if it goes up when the system is switched on. 

If you find a wiring problem and fix it, and check that the compressor pulley is turning the shaft (as suggested a few posts up), you've almost certainly got the compressor going. The place you took it to regas it would have told you if there were significant leaks.  Not sure that filling with compressed air is worth doing, you are likely to introduce moisture with it, which A/C systems aren't keen on.

12 hours ago, Wino said:

It's quite possible that the HVAC module and engine ECU 'chat' to enable exactly the behaviour you suggest.  I don't know if it does happen, but a VCDS logging session might spot it (vaguest of feelings I may have tried this and not found it, but that could've easily been something else).  Full beans on the loud pedal could easily be communicated to the HVAC module and the PWM'ed A/C flow control backed off temporarily?  Possibly only implemented on the more performancy variants, so possibly not on either my Polo or the missus's 3-potter.

That could be done, given a variant that has standard drive by wire throttle and aircon, and then a decision that this is desirable behaviour by the aircon. Given that Porsche regard aircon as desirable in a closed GT I'm not sure that it would be.

All Fabias are DBW.

Personally, I'd never ever attempt to fool any fridge system into operating the compressor by pressurising it using air.

49 minutes ago, rum4mo said:

Personally, I'd never ever attempt to fool any fridge system into operating the compressor by pressurising it using air.

 

Agreed, it's a terrible idea, you'd introduce a lot of water vapour into the system which is death to aircon compressors.

Duly noted, I'll stay clear!