How do I fix heater in Honda accord 1997 model Diesel?

The Heater in my Honda accord, 1997 model, Diesel suddenly stop working after the car had been parked for a period of about 3 months. I have topped the water level but still didnt work. Could it be a fuse link problem? or that of antifreeze?. The temperature in my country is now betweeen -4 and 8 degrees celsius. Please could any one help me out ?