I have a good customer with exactly the same situation. I agree with Gilly on the likelyhood of the duovalve, but haven't been able to catach the problem even though I have driven the car at least 40 miles.

I drove the car while monitoring the control signal to that side of the duovalve. With no problem I saw no problem.

The only thing the your data tells me is that the heater valve did go open, everthing else is fine. Whether it responded to a command or just did it is the last piece of the puzzle. On my car there the SDS did not show the command nor give capability to initiate the command.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician