a lot of reported faults lately appear to be related to the VERY VERY COLD weather,this is causing FREEZING in the condensate pipe.
check that you pipe is not frozen
try thawing the plastic pipe out with kettles of hot water or a hair dryer.
more insulation on the pipe is needed. increase to the next size of pipe over the existing pipe when the weather improves.
wirecutterman, January 2010