Air conditioner malfunction

Hello!

As is appropriate for the season, the air conditioning system in our family car has broken down.
Passat 3C
BJ 2008
140PS
Combo

For some time now, a hissing sound has been audible in the dashboard area during cooling operation. This sound has been getting progressively louder over time. Since yesterday, there has been no cooling performance at all.

Today, I quickly performed an auto scan, and lo and behold: Apart from a sporadic error in the right-side valve drive, there were no errors in the air conditioning system.
So, I've performed a reset - no improvement.

Refrigerant high-pressure side at standstill at approximately 25°C outdoor temperature, 5.3 bar. In operation, 8.6 bar.
One can easily notice that when the air conditioning is turned on, the engine is slightly strained. I assume that, therefore, (sufficient) refrigerant is available.

My repair approach: Removing the refrigerant in the workshop - then replacing the drier and expansion valve - filling the system and hoping it works.

To the Experts:

- Are there any other potential error points?

- Can I replace the expansion valve from the engine compartment in the 3C? Not all-wheel drive.

- Besides meticulous cleanliness, are there any other important considerations when installing the new valve? New O-rings or lubrication during installation?

Thank you in advance

Manuel

Increasing hissing sounds from the area of the evaporator can essentially be two things:
1) A leak towards the interior (then there should be more hissing while stationary, as the evaporator pressure decreases during operation) or
2) Incorrect fill volume and resulting flow or evaporation noises.

I strongly suspect that your coolant level is no longer sufficient, and therefore you are no longer achieving optimal cooling performance.

Theoretically, the expansion valve could also have failed. But without moisture ingress or without splinters in the system, I don't believe it initially.

Depending on the price, I would leave the existing valve in place and only fill it for now.

Greetings
Guste

Hello!

Alo, when the air conditioner is running, you should have approximately 13 bar in the system at 25°C. Approximately 6-7 bar at standstill.

Your compressor is disconnected via a magnetic coupling, or controlled via an electric valve? If that's the case, then let's take a look at the diagnosis to see what voltage the valve is actually being actuated with.

Causes (in my opinion):

1. Insufficient refrigerant (most likely)
2. Compressor faulty
3. Compressor Control
3. Expansion valve set to "Pass-through"


Best regards,
brezelmann01

Before you start swapping parts randomly, I would recommend getting them diagnosed first!

1. If the expansion valve is faulty, the line upstream of it will become pressurized, and the interior will not be cooled.
2. Is your climate compressor controlled by a magnetic clutch or by an electrically controlled valve?
3. When was the last climate check performed?
4. What shutdown conditions are listed - if any.

The pressure is too high. I experienced this with my own system, you could clearly feel the compressor turning on, and the motor seemed to work harder, but the system still didn't cool much more. Refrigerant absorbed --> 80g remaining. (from approximately 500g)
Refilling the system will only provide temporary relief. There are contrast agents that can be added to the refrigerant, which will then make the leak visible. **Definitely** use new O-rings and lubricate them during assembly.
If you know someone who works with cold, they have detectors that can detect even a few grams per year. This allows you to save the contrast agent (and, depending on the situation, also the filling in the workshop; however, you should know what you are doing ).

Adding a new filling to a known and leaky system with contrast agent clearly falls under the criminal code!

It is necessary to perform a leak test with a pressure of 25 bar using either nitrogen or Formiergas, then eliminate the leak and re-check for tightness!

I leave the system running overnight and observe how much the pressure drops. If it drops to 1 bar over a few hours and then remains stable, that's okay. If the pressure drops constantly, then you need to investigate further.

Following the price surge for R134a, it is also in the interest of car owners.

Hello!

Thank you for your responses and sorry for the late reply - I've been very busy lately.

Now I would like to return to the problem of air conditioning.

To the questions from vag-driver:

1.) No freezing in the valve area
2.) I am deriving the value from the compressor current (measured value) - which is approximately 0.8A - see image.
3.) Climate maintenance was over 2 years ago.
4.) There is no shutdown condition.

Manuel

Hello!

I'm not a climate control expert, but I did take a relevant training course.
It's also been quite a few years.

One has said, regarding the dryer:
One should palpate it with the hand while the machine is running.
If one side is cold, and the other side is hot,
it would be saturated, and it would need to be replaced. In that case, not enough is getting through. How is it clogged...?

That's very simple, just try it.
This could also be a reason why the air conditioner is not working.
Whether this is also the reason for the low pressure in the system, I don't know.

Hello!

Short update: The car was at ATU for a climate service.
During the inspection, it was found that only 50g of refrigerant was remaining.
The system was then filled with inert gas, and it appeared to be airtight. Therefore, new refrigerant has been added and it's complete.

Manuel

How long was the overpressure in the system maintained, overnight?

Manuel82 wrote:

During the inspection, it was found that only 50g of refrigerant was remaining.

I hope additional contrast agent has been added. 50g of the remaining amount seems suspiciously little to me.

One often finds such a small remaining amount if the loss was caused by rockfall or a worn-out seal. It remains to be hoped that the price for a filling will be justified by a sufficiently long pressure test.