REMOVE ALL POWER TO THE BOILER!!!!!!!!!!!!!!
1. Remove the lower cover by pulling forward and down. No screw removal required.
2. Loosen 4 long brass coloured screws holding the main cover in place, one at each corner, top and bottom. Remove cover by pulling forward.
3. Fan is at the top mounted vertically. The usual problem is the impeller blades are hitting the top of the housing, either because of worn bearings or aging rubber mounts.
4. Before you replace the fan, it might be fixed by gently prying the impeller upwards around the circumference to slightly bend the impeller blades upward and lift it from scraping or binding on the lower housing. Give it a spin with a screwdriver and make sure it doesn't scrape on the housing. 1/8 inch clearance should be adequate.
5. Total cost of repair 0. Time 1/2 hour. Tools, phillips screwdriver and flat screwdriver to pry impeller.
john
December 2012