Golf 4: Low AC Compressor Pressure - Troubleshooting

Hey.

I have a Golf 4, manufactured in 2001, with a 1.4L engine and 75 horsepower. It has manual air conditioning.

I just refilled the refrigerant.
- No function.

Error code read.
16916 P0532 Air conditioning pressure sensor (G65), signal too low.
Replaced the pressure sensor as a precaution, but that wasn't the problem.
The error keeps happening every time I turn on the air conditioning.

Measurements indicate everything is within normal limits. Compressor status: ON.

Voltage at the compressor's power plug checked: 4-6V.
When a 12V voltage is applied, the magnetic coupling works perfectly.

Fuse 16 and the fuse block on the battery have been checked and tested.
Everything is fine.

Checked the cables from the compressor to the fan control unit.
Cables are in good condition.

Replaced the fan control unit with a used one.
No improvement.

Does anyone have any other advice?

First, check the cables and connectors for oxidation or breaks.
Without a proper signal from the pressure sensor, the compressor will most likely not be activated.

Also, pull out the 30A fuses above the battery and check if they are burnt. This can happen occasionally until the air conditioning system fails completely.
Otherwise, as others have already mentioned, please proofread.

All cables, connectors, and fuses have been checked again. Everything looks fine.
I've checked all the mass points again, and there's nothing to note.

What I've realized now.
The green/black wire on pin 10 of the fan control unit goes to the air conditioning compressor. It has a constant voltage of 6V even when the ignition is off.
The same 6V that are also used when the ignition and air conditioning are turned on.

Isn't that unusual?

I've also checked the front fans, and both are running in both low and high speed modes.

Is there a way to test whether both fan control units I have are defective?

Should the fans start immediately when I turn on the air conditioning, or only when the pressure in the system increases?
These remain off when the climate control is turned on.

The fans should turn on when the air conditioning is on. Please check the voltage at the input of the fan control unit (FCU) on the thick cable that comes from the fuse located on top of the battery; measure there! It's possible that the FCU or the cable lug connection has burned out and has a poor connection. If you measure 12V at the input under load and 6 volts at the output as you described, then the problem is likely there.