I am battling about the same issues.
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I tested the dc-dc converter externally at the connectors for blown 40 amp fuses. Seemed to all check out. The 13.4 volt voltage was present at the negative and positive coming off the dc-dc.
I'm not sure what the BMS_ f027 warning is or the Dl_u014. Anyone else clue me in?
The AC was working but the heat (PTC) I am unsure. The interior blower was working but surging and then quit altogether which now leads me to go back and retest dc-dc fuses...
Ok, interior blower motor back to working but it somehow feels like a draining battery issue even though I have 13+ volt power off from dc-dc but tonight no ac compressor or heat and it doesn't like running the interior fan very long
Car out of warranty they say. It's a 2012 S 85.