Drain juice from clams into a large skillet over onions, celery, potatoes and carrots. Add water to cover, and cook over medium heat until tender.
In a large, heavy saucepan, melt butter over medium heat. Whisk in flour until smooth. Whisk in Half & Half and stir constantly until thick and smooth. Stir in vegetables and clam juice. Heat through. Do not boil.
Stir in clams just before serving. Do not overcook clams. When clams are heated through, stir in vinegar, and season with salt and pepper.