Problems with ventilation and manual air conditioning

Hello everyone,
============
I have a very strange problem and I'm hoping for some helpful advice.
Often, it's just an idea and the necessary experience that helps you move forward.

The following has been verified and ensured:
Please provide the German text you would like me to translate into English.
- Toledo, model year 1999, AFN engine.
- Manual air conditioning system, filled and leak-tested.
- Fuses 6 and 19 are in good working order.
- The magnetic coupling engages, but not always... see below.

Problem:
Please provide the German text you would like me to translate into English.
- AC switch off, fan set to 1 => fan does not run.
- AC switch off, fan on positions 2, 3, 4 => fan runs on positions 2, 3, 4.

- AC switch on, fan off => air conditioning off... which, in my opinion, is how it should be...
- Turn on AC switch, Fan 1 => Fan does not run, air conditioning is working.
- Turn on AC switch, fans 2, 3, 4 => Fans 2, 3, 4 are running, air conditioning is not running.

When the fan is set to position 1, I can turn the air conditioner on and off using the AC switch.
However, the blower is not starting up. In switch position 2, 3, and 4, I can use the AC switch.
Do not turn on the air conditioning. The magnetic coupling is not engaging.

Unfortunately, I don't have a wiring diagram for the air conditioning system or the vehicle. A pressure sensor.
shouldn't be the cause either, since the pressure levels in the air conditioning system are normal.

Has anyone experienced this "phenomenon" in a VAG vehicle with a manual transmission?
Did you have the air conditioning on, or does anyone have any other clever ideas, or perhaps...?
corresponding circuit diagram? The relationship between the various...
I'm also not entirely clear about the fan speeds and the air conditioning system. Okay, fan zero and...
Turning off the air conditioner makes sense, otherwise the evaporator would freeze completely, but what about...?
is it in gear 2, 3, or 4?

It would be really nice if someone could help.

Best regards,
Andreas...

Have you ever measured the blower switch with a multimeter?

Your blower resistor might be defective.

As far as I know, the resistor is located in the passenger footwell, near the blower motor.

Martin R wrote:

Your pre-resistor for the blower motor might be defective.

Okay, here's the translation:

"Correct."

It must be the pre-resistance. The air conditioner is connected to the first setting of the switch, which is why it's running. The resistance between the first setting and the second (and all subsequent settings) is burned out, which is why the air conditioner doesn't work on the higher settings. Conversely, the faulty resistor between terminals 1 and 2 prevents the ventilation from operating on level 1.

For the Golf 3, it's a combined resistor (all three in one housing) that needs to be replaced entirely. It costs around 32€. Alternatively, you can also connect a single standard resistor between stage 1 and 2. For the G3, the values are 1.9 / 0.92 / 0.26 Ohms. It's likely that the values are similar for a Seat, so you would need to use a resistor of approximately 1.9 Ohms with the appropriate wire gauge. (10 Watts should be sufficient).

A complete replacement, while elegant and straightforward, is naturally more expensive.

Regards,
Guste.

Hello everyone,
==========
Thank you for the tips. Here's the translation:

"Especially the explanation about the series resistance."
It seems to be effective.

I would like to express my sincere gratitude and will provide an update.
if I had success using your tips.

Thank you very much for that.
Andreas...

Hello everyone,
==========
It was the initial resistance. I will post a repair description this weekend.
and link here. After visiting the doctor today, who...
Since the necessary resistor module wasn't available locally, I ended up doing the repair myself.
which took approximately 2 hours and cost around €2.60.

The air conditioning and fan are working again. More details will be available over the weekend.

Best regards,
Andreas...