check your pump.in the middle there should be a silver screw with a srewdriver slot in it, open this screw & put a screwdriver in the hole and give it a turn, as people do not use their heating in the summer months, it can get clogged & stick. do not worry if a little water comes out when you loosen the silver screw as this is normal. hope this cures your heating problem.
bob little, December 2010