Low air flow from forced air furnace?

Q: Hi, As the weather getting colder, I start to use the furnace (forced air) to heat my house. However, I notice the air flow from the second floor outlets from the furnace is smaller than before. Last year I could feel the air blowing from those outlets, but now the flow is quite small (the air flow is strong on the first floor though). The difference this year from last year is that I open up all the outlets on the first floor, while last year at least half of them were kept closed. My question is: Besides closing some outlets on the first floor, is there any other ways (like to get the furnace and air duct serviced?) to boost up the air flow for the second floor?

Many thanks!

A: Have you changed the furnace filter recently? They need to be changed periodically, every 30-90 days depending on what kind of filter and other factors.

A: If this is occurring only for second floor outlets, something could be blocking them. When I got duct cleaning done, two rooms magically started getting more air. If the second floor main pipe is blocked, ur first floor vents should be blowing more air now so check if that has happened. If that is the case, get ducts cleaned. However if it is a furnace specific issue like what Mike mentioned below, you should see a reduction in all ur vents (not only second floor).

Though closing 1st floor vents may get you more air on 2nd floor, I don’t think this should be used as a permanent solution if it involves closing several vents at the same time . I used to regularly close a few vents until the furnace person at my place recommended against it claiming it pressures outgoing airflow for the furnace and reduces its life (I guess it is probably still ok to close one or two vents but if you are planning to wipe out the entire 1st floor, then you may want to reconsider it over long term)