Originally Posted by diesel85
How did you reach this conclusion? Did you verify with anyone (i.e. MBZ tech or service dept)? I've been told that the aux pump should engage whenver the CCU is engaged. Also, I thought the aux pump forced water into the heater core when driving at low speeds or at a stop to prevent the cabin air from going cold while the wheel is heat mode (not just max heat mode).
With a meter and 3 different CCU's (engine running). It is difficult if not impossible to tell if the pump is running while the engine is on. The meter makes it possible to "see" when the thing actually comes on.
I would not trust a MB tech around here as far as I could throw them.
There may be some good ones out there. But, not in Melbourne or Ft. Pierce.