Power supply for Audi A4 B5 air conditioning

Good evening.

I have an Audi A4 B5, manufactured in 1995, with automatic climate control.

The car arrived with a newly filled, but non-functional, air conditioning system.
12V quick test on the compressor, running. No 12V power from the vehicle.

- Fuses checked.
- Relay measured, no terminal 30.
- Pressure switch measured, permanently open.

Okay, so I replaced the pressure switch, but it still doesn't work.

Error code (Sorry, I don't have my laptop for VCDS at the moment).

785, 799, 787, 779, 602, 601, 600, 604, 801, 797 - all resulted in a short circuit to the positive terminal.
All sensors/actuators are connected to fuse 25 or S225, which is a 30A fuse.

Fuses checked, the S15 10A fuse was suddenly defective, replaced, but no difference.

Mistakes cannot be erased.
On the high-voltage switch, I'm seeing 10.3V on pin 1, and on pin 2, which previously had 0V, I'm now seeing 4.53V.
Pin 3 has 12V as expected.

I'm slowly starting to feel desperate.
"The fuses are all fine, so why have I suddenly lost power?"

Does anyone happen to know the exact location of the A65 junction? Connector on the control panel?

Best regards.

Is the correct climate control system installed?

In 1995, the stepper motors were still powered by 7.2 volts, but later they were powered by 12 volts.

It's possible that a 12-volt control system (which often starts with the code 8L0 xxx xxx) has damaged something that can only handle 7.2 volts.

Toshi wrote:

G785, 799, 787, 779, 602, 601, 600, 604, 801, 797 - all of them short to positive

A short circuit to the positive terminal usually indicates a missing ground connection to the actuators/sensors. Was wurde geprüft?

It was due to a faulty control panel.

Toshi wrote:

Good evening, I have an Audi A4 B5, manufactured in 1995, with automatic climate control. The car arrived with a freshly filled, but non-functional, air conditioning system.

What is known about the background? I wonder who would fill an air conditioning system without performing a function test, just based on suspicion?