Cheddar Chowder

2 cups boiling water
2 cups diced potatoes
1/2 cup sliced carrots
1/2 cup sliced celery
1/4 cup chopped onion
1 1/2 teaspoons salt
1/4 teaspoon pepper
1/4 cup margarine
1/4 cup flour
2 cups milk
2 cups shredded sharp cheddar cheese
1 cup cubed cooked ham

Add water to potatoes, carrots, celery, onion, salt and pepper. Cover; simmer 10 minutes. Do not drain. Make white sauce with margarine, flour and milk. Add cheese; stir until melted. Add ham and undrained vegetables. Heat; do not boil. Serves 6 to 8.