W123

My heat has stopped working just in time for the cold weather! The temperature control unit works fine except for the complete lack of heat (the buttons all seem to do what they're supposed to). The heat gauge on the dash shows that the engine is getting hot, but none of the temp. control settings (defrost, bi-level, etc.) make hot air blow. The air coming out of the system is the outside temp.-frigid! I recently rebuilt the vacuum pump after the diaphram tore and a little oil got in the lines. But this sounds like an electrical problem, no?

I recently got the Mercedes factory HVAC manual, but I don't know where to start with this problem. I have the vacuum and wiring diagrams and now have a rough idea of how the system works (it's complicated!).

I have an '82 300D. When I try to start it, especially when it's cold, the starter works very slowly and feels like it is about to die. Seems like a dead or dying battery, but tested it and it's fine.

However when I hit the gas pedal when cranking, it does catch and start. This problem is especially harsh when the car is cold.

Do I need to replace the starter? Is there something else I'm missing? This car is my daily driver and I use it to cart my kids around and get to work, so I'm afraid to be stranded.

Thank you!