Honesty

What would you do in this situation?  You are a repairman who has been called to replace the water heater in the home of an old gentleman who is 88 years of age and cannot go downstairs where the water heater is located.  When you examine the water heater, however, you discover that only a minor problem with a setting is causing the water heater to malfunction.  A new unit is an unnecessary expense.  He will never know that the old one could be easily repaired, and you'll make many times more money.  After all, he did call and asked for the unit to be replaced.  Would you make the repair, replace the unit, or ask him to indicate just what he wanted done?