I have a 5 year old American Standard single stage Freedom 80 counterflow furnace. I have noticed recently in the morning when I turn the furnace on the draft inducer comes on it runs real long and then it shuts off like it could not get a vacum. It then comes right back on and acheives a vacum quickly and the furnace runs normal. The furnace then seems to run pretty much normal. Is it maybe because the vent is to cold and it is taking to long to get a draft ? or I am going in the wrong direction
Could have a leaking vacuum hose to the pressure switch or blockage in the port on the inducer fan/collector box it attaches to or failing switch. May have a blockage in the chimney or dead bird in the exhaust fan. Remove the smokepipe where it attaches to the top of the furnace and look inside for said dead bird or feathers (yes it happens).
"Cut it twice and it is still too short".
Thanks for your reply. I will check the vent I don't think a bird could be in there because I have hardware cloth over the cap on top but i will check anyway and thanks for your other advice I will keep an eye on it