If the fan is broken, would the heating and hot water still work?
check an see if there current to the fan
Don't use it!!! Trust me, you can cause more of a problem. Call a Professional to have it fixed.
Boiler ? fan? what kind of boiler uses a fan, except maybe for flue gases, and if that;s what is broke, call for service. Do not operate with faulty flue. Now, if again you're talking about a pump for water circulation, it probably will not work very well and could shut down on limit, because not many systems designed for a pump will work well on gravity feed.
