that means there is a bulb out somewhere on the exterior of the car.
the EC is short for economy, all functions of the limate control will work when it is pushed except the A/C compressor will never turn on.
the rest button when pushed on a cold day the car will remain warm for a short time air volume and distribution are controlled automatically.
i have never seen a thermostat rattle, is it the belt shock below the thermostat housing?