Just bought a 1984 300sd from a local guy with 188k on it. When i bought it i looked for common issues with smoke/ tranny/ coolant/ vacuum issues/ and electrical problems. Everything worked and it ran like a dream. ive owned the car for over a month now and the heater stopped working, doesnt even switch on when i hit the buttons, i think it may be the servo (makes a noise occasionally and sounds like a fan trying to get going). Secondly, the engines making a tapping/ popping noise on the passenger side, i hope that just means it needs the valves adjusted. theres a couple other minor issues but ill troubleshoot those later... any input about the heater and engine noise would be greatly appreciated.