Air Conditioner Condensate: Problems & Solutions

Hello,

"About 2 years ago, a manual air conditioning system was retrofitted to my car. A few weeks ago, I replaced the pollen filter and disinfected the air conditioning system (by spraying disinfectant through the intake channel after removing the pollen filter)."

After that, I hadn't used the air conditioning for about a week, but I drove a lot (so the normal ventilation was on).

Now I've turned it on, and after a few minutes, white steam suddenly came out of the central vents. The steam is odorless and I believe it's water vapor. As soon as you turn on the warm air or turn off the air conditioning, the steam disappears.

I've never experienced this before. What could it be? Possible explanations include:
Too much moisture in the ventilation duct.
1. Coolant from the heating heat exchanger - I'm ruling this out because there's no detectable coolant loss, and also the mist is odorless.

2. Disinfectant residue in the drain: This is possible, but it should have evaporated after 2-3 weeks.

3. Clogged water drain: Possibly. I once connected a hose there and was able to blow a little air through it. So, not completely clogged. Maybe slightly clogged?

Question: Does anyone recognize this problem? Could it also be something else, such as the climate not getting cold enough, or other types of damage?

Hold a smooth, flat surface in the steam and see if it condenses. Then you can tell what it is.

The water vapor is caused by high humidity and a too-cold evaporator, which operates in the sub-zero temperature range. Normally, a temperature sensor is installed near the evaporator to prevent the temperature from dropping below 2-4 degrees Celsius. Also, the expansion valve may be defective. Check the average discharge temperature of the nozzles. The target value for an outdoor temperature of 20 degrees Celsius is 2-78 degrees Celsius at a medium fan speed.

T3Surfer wrote:

The water vapor occurs when the air humidity is high and when the evaporator, which operates in the sub-zero range, is too cold! Normally, a temperature sensor is installed in the area around the evaporator to prevent the temperature from dropping below 2-4 degrees Celsius!

"No, definitely not in the Golf 4. Even my Audi 80 has a power-controlled air conditioning compressor (purely mechanical, based on the pressure ratio between the high and low pressure sides). This ensures that the temperature at the evaporator never drops below 4°C."

@Holger247: Has this been happening consistently since then, or was it a one-time occurrence?

Hello,

Thank you very much for the answers.
@wolfi_b:
Unfortunately, this has been happening consistently, and I'm now hesitant to even turn them on.
So, if I set it to the coldest setting, it stays at that temperature for the entire journey, as soon as the system starts and delivers full cooling.

A few weeks prior, I had measured the temperature at the central outlet, but the problem hadn't existed yet (at level 2, it was approximately +7°C).

As I understand it, the steam is created by high humidity.

When the air becomes warmer (by adjusting the heating), it can absorb more moisture, and no steam or fog will form.

Normally, the humidity that the warm air being drawn in contains "too much of" should condense on the evaporator and then disappear through the water drain.

If there is too much moisture, it won't work.
Or is the atomizer too cold?
Or is the moisture located behind the evaporator?

Hi wolfi_b and T3surfer,

I connected the thermometer again today, and it seems like you diagnosed the problem correctly. The temperature dropped much further than on my previous measurement, down to 5°C at the center outlet. Below 6.5°C, it started to steam slowly. => This indicates icing of the evaporator.

The installation manual for the air conditioner does not mention a temperature sensor on the evaporator (no cable connection). How does the control system then work?

Does the system disable the magnetic coupling as soon as it gets too cold?
An die Ansteuerung der Magnetkupplung gehen zu einen der Temperaturschalter des Kühlwassers (Bei Überhitzung), und ein sog. Dtraffic monitor.
I'm not sure whether the pressure sensor is used for the control, or whether it works "purely mechanically within the compressor," as wolfi_b suggested.

According to that, my compressor would be broken (which would be really bad after only 2 years and 2 months).

If there is no temperature sensor installed on the evaporator (since yours is an aftermarket addition, I'm not entirely sure), the temperature is regulated by the expansion valve and depends on the type of compressor, whether it's controlled or not. If you suspect the expansion valve might be defective, I would recommend replacing it first, as it costs around 35€. The compressor costs significantly more! Before removing it, the refrigerant must be extracted. A climate workshop might offer a reasonable price for checking, extracting, replacing the expansion valve, evacuating, and refilling the system.