Climatronic: Heating Only Mode Explained

hello,
I'm new, I'm not a mechanic, and I'm completely lost!

We have a Golf IV TDI with 90 horsepower. The Climatronic always blows hot air - it never produces cold air, even when set to the lowest temperature.
The heating temperature cannot be adjusted; there is no difference between setting it to 18 or 28.
Regardless of whether the setting is "auto" or "econ," only the outside temperature will be considered as the lowest temperature when the temperature is set to "low."

"The mechanic checked the system and found no error codes, and no repairs were performed on the system, but it simply stopped working suddenly."

The self-diagnosis also doesn't show any error codes. I put the Climatronic into diagnostic mode using the combination of "recirculate" + "warm" + "econ" buttons, which can be exited again by pressing "econ". Using the temperature buttons, you can then cycle through 256 values (two-digit hexadecimal numbers) on the right side. On the left side, you see values from 1 to 3 digits, in the range of 0 to 255. Unfortunately, I haven't been able to find any information anywhere about how to interpret these values.

The friendly person said: "The control unit is defective."

I'd like to know if the control unit could be the cause of this behavior, and whether this type of defect is common. Also, I'm interested in whether it's better to buy a new or used control unit, what the maximum cost should be, and whether it's better to have it installed professionally or if I can install it myself.

Okay, I can also imagine that the problem is with the control panel.
I would like to run the tests again and perform a basic calibration.
Perhaps a faulty servo motor can be identified in this process! However, if it's turning to the low position when cold and then fully heating up to 16 degrees, I highly doubt it's a defective servo.

Perhaps there's just a faulty sensor. As a test, let the car cool down and then check the sensor temperatures.

Perhaps it's just a faulty sensor. As a test, let the car cool down and then check the sensor temperatures.

It happened to me once too... The interior sensor was defective. It was always showing -54 degrees Celsius, and the heating would turn on because of the outside temperature of a balmy 30 degrees Celsius.

Hi,

"The same thing happened with my Ibi 6K. It was affected by the outside temperature. When it measured 40 degrees Celsius, it wanted to cool down, not heat up, even though it was -5 degrees Celsius in the winter."

Best regards,

Jan.

The first thing you should do is PROPERLY read the error codes using a genuine diagnostic tool. At the same time, you should also check the deactivation conditions, meaning you should see what the control unit indicates as the cause for the system not working. This will allow you to avoid guessing and blindly trying things like "could be/should be/ought to be."

hello,

Thank you for the answers.

in detail:
"The friendly technician used his diagnostic device to read and test the system, and after about 15 minutes, he told me that he had run all the tests and that no error could be detected. When I asked if a sensor might be defective, he said that the diagnostic device would show that, and since it didn't, he assumed that the problem is with the control unit itself."
He also conducted a basic system check, as he mentioned, but it yielded no results.

Can I assume that all sensors are working correctly if the diagnostic device doesn't report any errors?

and that brings me back to the question of purchasing a new or used tax device.
What is recommended: new or used?

gogo wrote:

In response to my question about whether a sensor might be defective, he said that the diagnostic device would indicate that, and since it wasn't, he assumes it's the control unit itself.

Incorrect. A faulty component doesn't necessarily have to be detected - again, please review the shutdown conditions!

gogo wrote:

He also conducted a basic adjustment, as he said - without any result.

There's no such thing as a neutral outcome; it either works or it doesn't.

gogo wrote:

Can I now assume that all sensors are in order if the diagnostic device does not report any errors?

No.

gogo wrote:

and that brings me back to the question of purchasing a new or used engine control unit. What is recommended - new or used?

Neither/nor, first, properly search for errors.

hello,

Thank you again for your patience.

When I said "with no result during the initial setup," I obviously meant "without any incorrect results," meaning "it worked." I will try to be more precise in my wording in the future.

Due to the shutdown conditions, I will be going to the service center again.

I'll get back to you soon with the results!