190E Rotary Heat Knob issue.
 

My 1988 190E is fitted with the three-rotary-knob setup below the blower and A/C switches on the centre console. I had a blown globe issue so I dismantled the console to sort the globe. That was easily sorted, but I discovered that the plastic square peg that joins the RH heat knob metal shaft to the heater box has sheared, meaning that temp on that side of the car cannot be selected even though the knob still turns through it's temp settings.
The plastic peg is a long black rectangular part with two articulated plastic joints at the heater box end which join to the heater box control with two round discs. The back of the rotary knob is inserted into this hollow square plastic peg via a corresponding square section metal shaft in a ball joint setup allowing for rotary movement.
Does anyone know if this plastic peg is serviced as a spare by MB and how is it removed from the heater box? Cannot find any info online only info on the climate control switch pack which mine doesn't have. Nothing in manuals either...
I may have to come up with a fix of my own...
Cheers...

I'd try a junkyard or ebay for a donor module. Otherwise, when plastic parts break at stress points like that, I've had good luck reinforcing with steel wire and then copious amounts of CA glue. Post a pic!

A pic will definitely help, are there any part numbers for the items that you're looking for? If so, please provide them and we can follow up with you if there's a match.

To the best of my knowledge the parts behind the knobs are all on one whole piece that is "meant to be" replaced as a whole.