Greetings, everyone! I am experiencing a perplexing problem with my 2018 Mercedes Vito Minibus W447.
I have been experiencing random fluctuations in the temperature gauge. This weekend, I undertook an extensive 15-hour drive, and here are my observations.
Temperature decline: When travelling at a constant pace of 70 mph or maintaining a consistent RPM, the temperature gauge will remain at the standard 90 degrees. However, when I attempt to activate the heater, it emits frigid air. Upon momentarily releasing the throttle or shifting into neutral on downhill gradients, the heater resumes heating, while the temperature gauge descends to just over 40 degrees and fluctuates between 40 and 80 degrees for approximately one minute. There will be a little fluctuation before stabilising around 80 degrees and ultimately reaching 90 degrees when I resume normal driving. The heater will remain warm for around 15 minutes, sufficient to provide warmth once more.
The temperature rises: When travelling at a steady motorway pace (50-70 mph), the temperature gauge remains normal at 90 degrees; however, upon applying additional power, such as during overtaking or ascending a hill, the gauge exceeds 90 degrees. I would hear the fan activate. The amount of power applied, the incline of the slope, and the duration of power application will influence whether the temperature reaches 120 degrees or above. However, it will descend rapidly when I reduce the throttle.
When the temperature exceeded 120 degrees on the freeway, I had a complete loss of throttle response; regardless of my actions with the throttle, the van did not respond and began to decelerate. I had to stop on the hard shoulder for a few seconds, and it was only after the temperature approached 90 degrees that I regained throttle control.
I have replaced one thermostat, but it did not yield any improvement.
I possess a Xentry device, and no fault codes are displayed. I lack mechanical expertise, hence I am unaware of what to observe. Any assistance would be greatly appreciated.