I'm sorry, but there's no such diagram that I could send you even if my life depended on doing so. I only wish it was that simple :-(
Let's start with the acronyms:
CAN stands for controlled area network which is the communications protocol the computers/modules in your car use to talk to one another.
SAM stands for signal-acquisition and actuation module which is the module that in this case receives the signal from the A/C control module to activate the auxiliary coolant pump.
Basically, your Mercedes is full of computers or modules; some you interact directly with (EX: HVAC control module, power window control module, etc.) and some you don't (EX: SAM, etc.)
To repair the issue with your heater, a dedicated computer/scan tool must be plugged in so it can communicate through the CAN network with the HVAC and SAM modules involved in activating the auxiliary coolant pump to see which command signal or actuator is not working as it should.
In other words, as I stated in my introduction, I have and I'm willing to provide the technical knowledge you'd need to handle this issue yourself, but to complete the job you'd need to provide the tools and skills to use them.
Now, if I were to give an educated guess, I'd say the most likey cause of the symptoms you describe would be between the auxiliary pump and the right front SAM - all you would have to do is use a high impedance voltmeter to check for voltage at the aux pump when you select heater on the A/C control panel. If there is voltage, the SAM is OK and the pump is the issue. However, if there is no voltage, chances are the aux pump motor failed and when it did, it drew more current than the SAM could handle and damaged it as well.
I don't mean to confuse you with any of this stuff; it's just what wsome of us techs face every working day.
Please let me know if you have any other questions.