For comparison, the 1.5 tsi engine somehow warms up to a working temperature of about 90°C at an outside temperature of about 5°C at about 5km. The engine oil warms up later, reaching a temperature above 50°C is reached between about 10km, after about 25km the oil warms up to close to 90°C. This data can be seen on the Instruments cluster: The next step could be to somehow check the inlet and outlet temperatures of the coolant from the car cabin, in the case of hot pipes, the causes could be in the cabin. Then only the causes in the cabin remain, such as sensors, the other is the engine flaps for temperature regulation, control electronics,.... A long time ago I had an experience with the cabin temperature regulation, it worked once, the other time it didn't, with the air conditioning on it started blowing hot, when heating it started blowing cold at some point which would mean a breath of fresh air, hot or cooled. When connecting the vcds diagnostics, I found an error for the flap motor in the car's cabin. For anything more specific, better diagnostics would be needed, sensor temperatures, values and positions of the flap motors,... Certain sensors are also visible in the climate menu on Information Electr., which can be accessed by clicking on "menu" on the climate module. Some basic diagnostic steps can be done using these menus. This picture shows the connections that heat the cabin, if everything is ok one should be hot, the other slightly cooled. The hose connection should be located around the turbine.