Outside temperature display malfunctioned

After my ignition switch was replaced at the workshop, the outside temperature display on my dashboard stopped working. The temperature reading obtained through VAG-COM in menu point 01-Engine is normal.
Does anyone know how the temperature gauge is wired and whether it's possible to use a VAG-COM device to check if the temperature reading reaches the dashboard?




Audi A4, 1.9 TDI.
Year of construction: 1997.

Hi,

It's likely that your A4 also has a temperature sensor with 2 sensors on the coolant housing: one sends the temperature reading to the engine control unit (ECU), and the other sends it to the instrument cluster.
This temperature sensor has 4 connections. Check with a VAG-COM diagnostic tool what is displayed in the corresponding measurement block of the instrument cluster. If only a default value is shown, then either there's a break in the wiring somewhere or the sensor itself is simply defective.

Best regards, Rainer.

*whisper to @rainer* it's about the outside temperature, not the engine temperature.

Quote:

Does anyone know how the temperature gauge is wired and whether you can use VAG Com to test if the temperature value reaches the dashboard?

You might be able to display the outside temperature on your climate control system's screen. If something is displayed there, then the sensor itself is likely working correctly... The problem probably lies with the instrument cluster.
I don't know how it is with the A4, but on the A6, the outside temperature sensor is located behind the front bumper.

Oh .

Those who can read are at an advantage.

Quote:

I don't know how it is with the A4, but in the A6, the outside temperature sensor is located behind the front bumper.

"It's the same on the A4. It's located about halfway to the left, right in front of the radiator. If you remove the middle panel at the bottom of the bumper, you might even be able to reach it."

And what happens if my temperature sensor malfunctions and the temperatures fluctuate constantly?
Sometimes down to -40 degrees Celsius or even lower...

Does this affect my engine control unit (ECU), or just the climate control system?

As long as your car's internal sensors are only providing you with incorrect temperature readings, there's nothing to worry about.
If the coolant temperature gauge is malfunctioning, it's definitely worth replacing.

If the coolant level is okay, then everything should be fine.
thank you very much

Check the measurement groups in the combination instrument; you'll find the corresponding values for the outside temperature display there. It should not be of interest to the engine control unit in your vehicle, but the -40°C value you mentioned also indicates a short circuit (to ground).

Okay, so it means the thermometer itself isn't broken, but there might be a calibration error in the combination instrument?
"And can I read that information through the connection in the car?"

d-low wrote:

So, that means the thermometer itself isn't broken, but there might be a measurement error in the combination instrument?

Yes, but that needs to be verified; it's just a clue, not conclusive evidence.

d-low wrote:

...and can I read that information through the connection in the car?

As I said... double-check the sensor groups in the combination instrument and then use a multimeter to test them directly.

Hi,

It's likely that your A4 also has a temperature sensor with 2 sensors on the coolant housing: one sends the temperature reading to the engine control unit, and the other sends it to the instrument cluster.
Best regards, Rainer

Hmmm, measuring the outside temperature on the cylinder head... something new .