Climatronic: Outlet Temperature at "HI" Setting

Hello!

"The heating in my Octavia, manufactured in 1999 with an 81kW TDI engine, isn't working properly. Even with the Climatronic set to "HI" and after a long drive on the highway, the maximum outlet temperature of the heater is only about 60 degrees Celsius. When the car was new, I measured 75-76 degrees Celsius. The outside temperature during these measurements was below 0 degrees Celsius."

The thermostat has been checked, and the coolant temperature is above 88 degrees. When reading the error memory of the climate control system, the code "4FA" appears repeatedly, which, according to my table, indicates the "actuator motor for the bypass flap." Could this be related to the low outlet temperatures?

Meine Werkstatt stellt sich übrigens dumm, der Meister hat die Hand hingehalten und gemeint "kommt doch warm raus...". Irgendwelche Tipps für mich? DThank you!

Martin.

Did you measure that while driving on the highway?

It could indeed be related to the bypass valve. If the air flows "faster" through the heat exchanger than it can warm up through heat transfer to the heat exchanger's temperature, the measured outlet temperature will be lower.

However, if the problem wasn't with the diverter valve, I wouldn't worry too much about an outlet temperature of plus or minus 10°C when heating at maximum, as there are many factors that can influence it.

How did you even come up with the idea to measure it like that? Do you have any complaints if you set the Climatronic to, for example, 22°C?

Regards,
Malte.

Malte1408 wrote:

Did you measure that while driving on the highway?

Yes. I have a calibrated precision thermometer, and I inserted the sensor deep into the left air vent. I did this years ago (out of curiosity) because I wanted to see how the climate control system works, and I kept the readings. On the highway, it was consistently at 75 degrees, and after a minute of city driving, it dropped by 3-6 degrees, probably because the TDI engine doesn't generate enough heat in city traffic.

Quote:

It could indeed be related to the bypass valve. If the air flows "faster" through the heat exchanger than it can warm up due to the heat transfer to the heat exchanger's temperature, the measured outlet temperature will be lower. However, if the problem wasn't with the diverter valve, I wouldn't worry too much about an outlet temperature of plus or minus 10°C when heating at maximum, as there are many factors that can influence it. How did you even come up with measuring it that way? Do you have any issues if you set the Climatronic to, for example, 22°C?

"Yes, at an outside temperature below -10 degrees Celsius, it was impossible to get the car warm. When I noticed this, I checked the temperature again. What's strange is that the behavior I saw before now occurs at 61 degrees instead of 75 degrees... on the highway, it's a constant 61 degrees, and in the city, it's 55 degrees. Apparently, the 75 degrees from before were also regulated (otherwise, they wouldn't have been so consistently stable; there were only a few tenths up and down). Now, the car regulates to 61 degrees (very consistently). Interestingly, on one of the channels in the Climatronic service menu (23 and 24), you can see the target and actual outlet temperatures. At "HI," the target is 81, and the actual temperature is 61..."

Martin.