I believe only fan speed.

Heat might be thermostat, heater valve, clogged heater core, temp sensor in hvac system, or the hvac control itself. Possibly air in the system if it’s been opened up.

Any maintenance history? I recently had a new water pump that had the impeller installed backwards from the manufacturer. Got little flow to the heater core causing my issue.

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2000 E53 4.4
2011 E70 35d