Heat turned on -strange smeel - no heat

1989 XJ6. Turned the heater on. Strange smell (like burning plastic) and now no heat. Also, the engine temp. does not rise up much above 50 on the dash and the car has rough idle on startup. Where do I start?

1989 XJ6. Turned the heater on. Strange smell (like burning plastic) and now no heat. Also, the engine temp. does not rise up much above 50 on the dash and the car has rough idle on startup. Where do I start?
Is the coolant filled and bled? Could the smell be anti-freeze? The oil cap shouldn't have grayness, it's a sign of a blown head gasket. No heat points to the thermostat, which would restrict flow, bias the coolant sensor and cause engine to run rough. Temps would run hot on one side and ambiant on the other. Heater cores can become blocked, shut heat, but shouldn't cause poor engine running. Hope this gives a few hints!