Another update.

This weekend I replaced the heater core with a new Nissens one. Dash was that far open so...might as well right?

I also got the diaphragms installed into the vacuum pods and replaced in their respective locations. Tested vacuum on all the lines, everything looked good, dashboard back in.

The instrument cluster gave me problems with no backlighting. I ended up unplugging it and removing the potentiometer. I disassembled the potentiometer, gave it a thorough scrub (made the parts shine) and reassembled. Now it works perfectly.

On the engine side, I replaced the timing chain tensioner since mine had the original and they were prone to failure. Also got my Euro headlights and corners installed. Unfortunately, I broke one of the headlight trim moulding mounting tabs upon their arrival (NOS Hellas...fml). I ended up plastic welding the tab back on after epoxy and plastic cement failed to hold it in place. The angle is just a tad shy of being correct, so I had to run a machine screw with a washer and nut next to the hole it should go in. I'll get a better one from the hardware store to make it look correct when I go next time.

I'm now having a different issue with the climate control. Despite vacuum being good on all the lines, still having issues. I'm not seeing the control rods actuate or the vents change when I select the different settings on the climate control unit.

Based on this guide (Troubleshooting the Mercedes-Benz 190 Tempmatic ACC Climate Control System) I checked the resistance on the plugs for the 4 and 5 port switchover valve. All but hole 1 on the right hand connector had the correct ohm reading.

I also tried to check the voltage on the feedback potentiometer as described in the guide and that was fine.

Lastly, when I handled the climate control unit, it would flicker and things would cut in and out.

Just not sure where to go from here (is the climate control unit itself bad? Is it the switchover valve unit?).