Comfort Module Error: Troubleshooting Guide

Vehicle: Volkswagen Passat TDI 3B, manufactured in 1998.
Hello everyone, I've been having two errors in the central module's comfort system for quite some time now:
1. Mirror heating on the passenger side is faulty.
2. 03A2 Rear left central locking latch unit - signal implausible.
Here's the translation:

'Regarding item 1: When I turn on the mirror heating, the left-hand mirror becomes noticeably warm. The right-hand mirror only becomes lukewarm. The voltage at the right-hand mirror is 12.1 volts (with the ignition on, without the engine running, measured directly at the connectors on the mirror glass), and the resistance of the heating element is 135 ohms.'
Is the mirror heating malfunctioning?
Does the entire mirror need to be replaced?
Regarding item 2: Only the remote control function of my central locking system is not working; all other functions are working perfectly.
The following has already been checked:
- Replaced batteries in the key.
- The spare key doesn't work either.
- Someone has programmed a foreign key into my code.
- Encoding verified.
- The door close signal is the same for all 4 doors (when a door is opened, it shows 3.8 volts for approximately 3-4 seconds, then returns to 11.8 volts, only when the ignition is on).
Could it possibly be a bite from a weasel?
Could the door control unit be defective (on the wiper motor)?
Is the ignition cylinder switch faulty?
Is there a problem with the central module (the radio receiver)?
I would be extremely grateful for any information you can provide.
Best regards,
Kradmelder.

Hello,

Regarding the heated mirrors, there is a post about it in the bodywork forum.

The error in the system is likely number 930, right?
This can have the following causes:

faulty cables or connectors => check the cables.
Power supply to the central locking system at the rear left door is missing => measure.
Mechanism in the locking unit and operating parts is stiff/difficult to move => Check the mechanism.
Rear left door control module (F222) defective.

Due to the radio remote control:

Insert the key into the ignition and turn it to start the engine.
Using a different key from the outside, repeatedly engage the lock in the locked position for a while.
Then, operate the unlocked door for a while.
Finally, re-engage the lock to its closed position.

Hello Michal II,
Thank you for the prompt response. I will test a few more things tonight, especially regarding the keys (encoding).
Just to reiterate: All the functions of the central locking system work when I use the key in the door lock to close it. The power supply voltages and the voltage for opening/closing the doors are present.
Question about the mirror heating: You write that in 99% of cases, the mirror glass itself is the cause. That's probably true, since there's a voltage of 12.1 volts applied to the glass. But could it be technically possible for the glass to become only lukewarm, but not as warm as the left side? The resistance is 132 ohms.
Can the glass be replaced separately? Can the mirror be disassembled? Or does it have to be replaced completely? Approximately how much does the replacement part cost?
Best regards,
Kradmelder.

Hello,

The mirror glass (including the mounting plate) costs approximately 31 EUR.

Numbers:

From serial number 3B1 857 522 up to and including serial number 3B-V-100000.
otherwise:
3B1 857 522 C

hi
I once had a problem with a remote control that wasn't working. In the car, the electrical part of the ignition switch was broken. Check if the 'S' contact is switching properly. In my case, it stopped disengaging, which meant the voltage was always on, and as a result, the remote control wouldn't work.

Hello Micha II,
I'm absolutely thrilled. Thank you so much for your expert help. The radio control system for the garage door is working again after I recalibrated it according to your instructions.
I had been dealing with this issue for about 6 months and had contacted four different Volkswagen specialist workshops in the meantime. None of them were able to help me. If it had been up to them, I would have already replaced half of the vehicle with new parts.
What also frustrates me is that the procedure for reprogramming the ignition key, as described in the user manual, is completely different and, of course, doesn't work.
This forum has helped me before with an issue related to a faulty mass airflow sensor.
I think it's absolutely great!
Thank you again for your competent assistance.
'As soon as my mirror heater starts working again, I will let you know.'
Best regards, Kradmelder.

Hello Kradmelder,
If you measure 132 ohms on your exterior mirror, the heating element is definitely defective. Using the formula P = U²/R (where P is power, U is voltage, and R is resistance), we get: 13² V² / 132 ohms = 1.28 watts. This is certainly too low; the glass would likely not heat up noticeably.

Michael II wrote:

Hello, Regarding the heated mirrors, there is a post about it in the bodywork forum. The error in the system is likely number 930, right? This can have the following causes: faulty cables or connectors => check the cables. Power supply to the central locking system at the rear left door is missing => measure. Mechanism within the locking unit and operating parts is stiff/difficult to move => Check the mechanism. Rear left door control module (F222) defective. Due to the radio remote control: Insert the key into the ignition and turn it to start the engine. Using a different key from the outside, repeatedly engage the lock in the locked position for a while. Then, operate the unlocked door for a while. Finally, operate the lock

to ensure it is closed.
Hello Michael,
What do you mean by "operate the lock in the locked position for a while"?
Manually lock and press a button on the radio key?

Are there any known hardware defects?
My remote control is no longer working, but the central locking system works fine when using the key in the driver's door, as well as with the button inside the door.

Best regards,
Kurt.