Strange behavior of the air conditioner

Hello everyone,

In the spring of 2019, I bought a used Skoda 2.0 TDI 4x4, model year 2011 (3T5), from a colleague.
Shortly after purchasing the car, I had the air conditioning system serviced at ATU (my colleague had never had one done before). They told me there that the cooling performance was no longer 100%.

Here are the data from the climate service for June 2019:

Device: Waeco ASC2 000

Vacuumed. Filled.
Refrigerant: 390g, 550g.
Oil: 13 ml, 20 ml.
UV: 4 ml

As far as I understand, the climate functioned normally during the summers of 2019 and 2020.

In early 2021, the freewheel on the alternator broke, and I replaced it. When I first turned on the air conditioning in 2021, no cold air came out.

The assumption was that the defective alternator clutch might have also damaged the magnetic coupling or drive plate of the compressor. So, I replaced that as well. Unfortunately, it didn't work; there's still no air conditioning. Right after the climate service, it turned out that the air conditioning was working again.

Here are the data from the climate service for June 2021:

Device: ISC Silver Futura Diag

Vacuumed. Filled.
Refrigerant: 140g, 600g (so there was very little refrigerant in there).
Oil: 0 g, 10 g.

In the summer of 2021, the air conditioning system worked normally (although it felt a bit weak during periods of extreme heat).
Just a little over a year later, the climate isn't cooling down again. Okay, back to the climate service.

Here are the data from the climate service for April 2022:

Device: unknown.

Vacuumed. Filled.
Refrigerant: 414g, 525g (this time, not as much refrigerant was missing).
Oil: unknown, 5 g.

Unfortunately, there is no change, and the climate is still not .
"This is all very strange. When I press the AC button on the control panel, the green LED lights up." There were no error codes stored in the climate control unit's memory either.

I then had some values read out using VCDS.

Engine off, air conditioning turned off:
Address 08: Climate Control/Heating Unit (3T0 907 044 BA)
IDE00019 Voltage at terminal 30: 11.7 V.
IDE00021 Motor speed 0 RPM.
IDE00198-ENG100282 Refrigerant pressure multiplexer. Refrigerant pressure: 7.0 bar.
IDE00965 Compressor shutdown condition: AC button off.
IDE00966 Compressor current: Current value 0.000 A.
IDE00967 Compressor current: Setpoint 0.000 A.
IDE00968 Compressor speed: 0 RPM.
IDE00969 Compressor load: 0.0 Nm.
IDE00970-ENG103807 Cooler fan control, actual value multiplexer, fan control: 9.6%.
IDE00971 Cooler fan control: Setpoint 0.0%.
IDE00982-ENG103939 Temperature after evaporator multiplexer Temperature after evaporator 34.3 °C

Engine on, air conditioning turned on:

Address 08: Climate Control/Heating Unit (3T0 907 044 BA)
IDE00019 Voltage at terminal 30: 13.4 V.
IDE00021 Motor speed: 900 rpm.
IDE00198-ENG100282 Refrigerant pressure multiplexer. Refrigerant pressure: 7.8 bar.
IDE00965 Compressor shutdown condition: Compressor is active; no shutdown condition detected.
IDE00966 Compressor current: Actual value 0.820 A.
IDE00967 Compressor current: Setpoint 0.820 A.
IDE00968 Compressor speed: 1100 RPM.
IDE00969 Compressor load: 3.1 Nm.
IDE00970-ENG103807 Cooler fan control, actual value multiplexer, fan control: 9.6%.
IDE00971 Cooler fan control: Setpoint 0.0%.
IDE00982-ENG103939 Temperature after evaporator multiplexer Temperature after evaporator 31.0 °C
IDE02472 Climate Operations n.v.

If you directly activate the compressor via VCDS, there will be an entry in the error memory afterwards:

9480469 - Control of air conditioning compressor.
B10A9 15 [009] - Interruption/Short circuit after positive terminal.
confirmed - checked since last deletion.
Environmental conditions:
Error status: 00000001
Error priority: 2
Error frequency: 1
Lost Count: 225


Here are the actual values after the induced error:

Engine on, air conditioning turned on:

IDE00019 Voltage at terminal 30: 13.3 V.
IDE00021 Motor speed: 900 rpm.
IDE00025 Coolant temperature: 69 °C
IDE00198-ENG100282 Refrigerant pressure multiplexer. Refrigerant pressure: 8.0 bar.
IDE00965 Compressor shutdown condition Compressor control: Error in the control path
IDE00966 Compressor current: Actual value 0.075 A
IDE00967 Compressor current: Set point 0.000 A
IDE00968 Compressor speed: 1100 RPM.
IDE00969 Compressor load: 3.3 Nm.
IDE00970-ENG103807 Cooler fan control, actual value multiplexer, fan control: 9.6%.
IDE00971 Cooler fan control: Setpoint 0.0%.
IDE00982-ENG103939 Temperature after evaporator multiplexer Temperature after evaporator 30.3 °C

There are now changes to the parameters IDE00965 (Compressor shutdown condition) and IDE00967 (Compressor current setpoint).

I'm really at my wit's end. Who can help me here?

Greetings.
Roland.

Hello Roland,

Whether ATU is a good place to spend money is something that each person has to decide for themselves.

If, during every climate service, more than 100g of refrigerant needs to be refilled, then at least one part is not completely sealed .

At a minimum, the climate control system – perhaps even the technician who repeatedly fills the system without checking its integrity.



What is the pressure in the low-pressure (LP) range?

What is the pressure in the HP area when you turn on the air conditioning?

Is anything changing?

If there are no error messages, then either the system has a leak, or the compressor is no longer able to build up sufficient pressure, for example, because the compressor shaft is broken.
(Pre-damage free-running)

The error message might indicate a faulty control valve or, more typically in the SuperB, a corroded connector. A short circuit to the positive terminal can also be checked relatively quickly.

You will be surprised how much the pressure from the air conditioner helps you when loosening the control valve. - Keep your fingers away as long as the system is under pressure.

While a faulty control unit is theoretically possible, I consider it unlikely given the observed error pattern.

If contrast agent was present in the air conditioning system, it should be relatively easy to detect.


All further information will be available after the complete car scan.



Best regards,

Michael.

Okay, I'm ready. Please provide the German text you want me to translate.

I suspect a faulty air conditioning compressor. That's exactly what I had with my Sharan as well. The compressor load is not increasing!

Furthermore, I assume that you have a leak causing these discrepancies in the quantities. It's a good idea to locate these issues before replacing the compressor, so they can be addressed while the system is already open.

Quote:

It is useful to find these

before replacing the compressor, so that they can be removed when the system is already open.

The capacitor, if it's still the original one after 11 years, is very likely on the verge of failure. I would definitely exchange it.

Autoservice wrote:

The capacitor, if it's still the original one after 11 years, is very likely on the verge of failure. I would definitely exchange it.

It was definitely going to be replaced as soon as the circuit was open.

Okay, I'm back after our vacation. The repair was successfully completed at the workshop. In addition to the completely destroyed and leaking condenser, there was also the refrigerant line from the condenser to the compressor. It was completely stuck to the condenser (aluminum on aluminum). This line alone cost almost 300 euros (original VAG part). Due to the time constraints, there was no opportunity to explore alternative, more affordable options (such as used items or accessories).
In total, the repair cost me 1034.- EUR, even though I sourced the compressor (Mahle) and condenser (Valeo) myself at a lower price.
But the alternative would have been to go on vacation without air conditioning. And ultimately, we were glad that the climate was improving again.