Need some advice on Air conditioning diagnosis - Not blowing cold

Thanks Andy @Andrew for the label file and instuctions. All installed (my HVAC is actually 8Z2-820-043, not 8Z0. It is hard touch, and looks original, and has been working previously). My german is not great, but it looks like the same layout etc.

Does the label file have more than just text additon to VCDS?

What has shown up this morning is a 12 in the second box of Group 002. This I believe is '12 = Compressor OFF: Shut-Off requested by Engine Control' which is usual for startup until up to heat or the engine is ready for the load.
Thus my question about what a label file does. Does it change what data appears in the measuring block? I have not seen this block populated before.

This translates to Penultimate shutdown condition, or 'Last Shut-off Criteria' in english versions, so should not have any effect on the compressor current state.

Thanks to @a-zwo for the compressor comments. All parts of the pulley appear to be rotating, but I will take the belt off etc and have a look in detail. I have another compressor where the pully works, but the N280 does not, so can do some 'feel' comparison.

For some reason, even though there are no fault codes, and to me, all measuring blocks look correct and in range, I am thinking the intermittent comms issues have confused the HVAC controller. This is just a hunch, and is not really rational, but unless another sensor is 'lying', I can't think of any other cause (unless the Comp is b****red).

The only change I have made since known working is the CCCU (put the old one back yesterday, and the situation is the same), and a new upstream Lambda sensor.

I might ask the scrappers if they have a very poor (but working) HVAC controller I can borrow/buy to test it out.

Any bright ideas very much appreciated.

Matt
 
It doesn't change the data in the blocks, that comes from the controller, but it does give the correct descriptions for the data.

Do you see the new lbl file name at the top left of the screen, showing that it is being used?
Mac.
 
Hi,

You need a set of AC gauges and a multimeter with a frequency counting function to test the electronic solenoid on the compressor.

If the solenoid is being pulsed on at a full duty cycle and the high/low side pressures are not what they should be then you have to do more digging towards the right direction.

If there has been a previous failure then "black death" i.e., fine metal bits mixed with oil will have blocked the orifice tube. The orifice tube is inline with the ac line where two pieces join together with a bolt/flange. You can only know about this with a set of gauges.

Evros
 
PlasticMac said:
It doesn't change the data in the blocks, that comes from the controller, but it does give the correct descriptions for the data.

Do you see the new lbl file name at the top left of the screen, showing that it is being used?
Mac.
Click to expand...
Sorry, silly question above, you are obviously seeing the new lbl, as it's in German!
Mac.
 
If your controller software doesn't match the lbl file, being 8Z2-820-043, not 8Z0-820-043, that's odd.
Are you seeing the 8Z2-xxx on the screen, that is, read from the controller itself?
Mac.
 
8Z2 would just be right hand drive I would guess, so no issue.

@Evripidis even if the tube was blocked, wouldn’t the G65 high pressure sensor still change its value if the compressor was working at all?
 
Try unplugging it and see what the registered value is. If memory serves it is only a schrader valve. You van try and trick it using a potentiometer but I cannot remember what resistance values it will output. If you can see the changes via vcds then it means the wiring to the module is all all right.
 
PlasticMac said:
If your controller software doesn't match the lbl file, being 8Z2-820-043, not 8Z0-820-043, that's odd.
Are you seeing the 8Z2-xxx on the screen, that is, read from the controller itself?
Mac.
Click to expand...
Indeed, this is the code on the controller. Photo attached with the past connection fault. I had to change the name of the label file from Andy to make it show up in VCDS. I wonder if others have this software?
I am assuming it is legit A2 as it starts with 8Z.

It has all been working, so not sure the software itself is the issue.

Next step is to test what ampege and voltage are getting to the n280 valve.
 

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You can unplug it to check. I am 99% sure that the current shown is measured, therefore if you unplug N280 it will fall to 0.

If that is the case, either N280 is seized, or the compressor is seized
 
a-zwo said:
You can unplug it to check. I am 99% sure that the current shown is measured, therefore if you unplug N280 it will fall to 0.

If that is the case, either N280 is seized, or the compressor is seized
Click to expand...
I don't think unplugging the N280 will show a zero value. Unplugging it may give you an N280 failure code though, such as N280 Open Circuit, as the HVAC controller will, I'd reckon, detect an open circuit.
With engine running, have a look at HVAC Measuring Blocks, Group 001 and 002. Should give you a clue as to what's going on, or not ...
Mac.
 
PlasticMac said:
I don't think unplugging the N280 will show a zero value. Unplugging it may give you an N280 failure code though, such as N280 Open Circuit, as the HVAC controller will, I'd reckon, detect an open circuit.
With engine running, have a look at HVAC Measuring Blocks, Group 001 and 002. Should give you a clue as to what's going on, or not ...
Mac.
Click to expand...
You should see something like this, courtesy of @Andrew:

1713280810488.png


Mac.
 
PlasticMac said:
Here's a working one.
Mac.

View attachment 122687
Click to expand...
Thanks for the screenshot Mac

For how this compares to mine, and the other symptoms, I am definitely leaning towards a failed N280 solenoid. I have another on a compressor where I think the N280 has failed. It clicks when 12v is applied, but you cannot see the chrome rod move at all. I think the same has happened to mine, and the car is trying to move it, but is won't open.

The boxes 1 and 2 make me think the valve is being called to open, but it is not happening.

I have found one in eBay for about £28, and this is the only one where there is a cable, as opposed to a fixed 2 pin connector. I think I will keep the form factor, even though the other valves look of better quality. I can't find a part no. as it looks like the valve is offically part of the compressor, not a separate part.

Alas, this will mean a de-gas. The bloke is coming for 2 other cars in the family, but it will be another £50 down the drain (unless I can convince him to use the old gas in one of the other cars - or reload it).

@a-zwo the compressor clutch is sound, and it has not seized, so I think the actual comp is OK.

Will post the solution when it is resolved.

Thanks all for attention and help.

Matt
 
Oskar said:
Thanks for the screenshot Mac

For how this compares to mine, and the other symptoms, I am definitely leaning towards a failed N280 solenoid. I have another on a compressor where I think the N280 has failed. It clicks when 12v is applied, but you cannot see the chrome rod move at all. I think the same has happened to mine, and the car is trying to move it, but is won't open.

The boxes 1 and 2 make me think the valve is being called to open, but it is not happening.

I have found one in eBay for about £28, and this is the only one where there is a cable, as opposed to a fixed 2 pin connector. I think I will keep the form factor, even though the other valves look of better quality. I can't find a part no. as it looks like the valve is offically part of the compressor, not a separate part.

Alas, this will mean a de-gas. The bloke is coming for 2 other cars in the family, but it will be another £50 down the drain (unless I can convince him to use the old gas in one of the other cars - or reload it).

@a-zwo the compressor clutch is sound, and it has not seized, so I think the actual comp is OK.

Will post the solution when it is resolved.

Thanks all for attention and help.

Matt
Click to expand...
There is no clutch on the A2 AC compressor, it runs all the time, with flow controlled by the N280. If you turn the AC off, (Econ), the N280 reduces flow to around 5%, but never zero.
Have a read of this, page 59 on. You'll understand it a lot better then.
Mac.
 

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