I just purchased my home a few months ago, and the AC was sub par during the summer. Now that winter is here, the house is extremely uncomfortable (cold).

My furnace shoots hot air up to one main exit, then branches to the two sides of my home.

I discovered two hinges, one on each branch, one of which when I rotated it, provided air to one side of my home (as many may expect)

The other, no matter how much I rotate or which angle I rotate the lever, the other side of that ducts remains cold and no air is pushed to the other side of my home.

Is it possible/smart for me, as a new home owner, to try to dissemble the ductwork in the problem area to attempt to free the valve or any possible blockage? One friend of mine told me to cut a hole in the side, use a coat hanger to try to open it, and seal it with duct tape.


I noticed when looking at how I could take the duct off, there are no screws, just tabs. Please see attached picture.

Any help is greatly appreciated by me and my cold family :)

enter image description here


Things are still not working in our home. I tried all different combinations of the two dampers open and close to no avail. I also drilled a hole and used a rod to ensure the left (in the diagram) damper was open which it was. There were no other obstructions in the way.

We are still hanging out in 65 degrees at max in cold, so please keep the suggestions coming.

Edit 3

Thanks to all that helped! Unfortunately, even a pro could not identify the problem and we ended up replacing the whole furnace. We are now a warm family again but after a hefty price tag.

  • What type of house is this? Can you see the full run of duct work? If it goes into the floors, walls, ceilings, this task could become a bit involved.
    – shufler
    Dec 9, 2011 at 0:58
  • Thank you for your comment, yes the duct runs under the main level and up to the upstairs after branching off a couple times. The path does not redirect for a while after it splits to the two sides of the home (splits, then runs for about 25 feet before the next split)
    – Benny
    Dec 9, 2011 at 1:01
  • Nice picture! Is it that abrupt -- on one side of the wall it's warm and on the other (in your crawlspace) it's cold?
    – shufler
    Dec 9, 2011 at 1:53
  • Thank you! @shufler, yes, it's "hot" before the lever, warm after the lever, and cold on the other side of the wall (in other words, the further away from the lever, the colder it gets)
    – Benny
    Dec 9, 2011 at 2:27
  • 1
    Close the right side.. and find where the left side has air pumping out, or maybe somewhere else.. you need to track down where the air is escaping. Find the point where the air is pushing out on the left side.. then you have to work out where in between the two points (not blowing and blowing) the fault is occurring there, most likely a blockage . ... One way is to inject odourless smoke into to the system while it is pumping air and see where it comes out.. viola!
    – Piotr Kula
    Dec 14, 2011 at 17:07

4 Answers 4


Don't use duck/duct tape on HVAC ducts, use foil tape. Duct tape isn't designed to take the heat variations in duct work and will lose it's adhesion over time.

foil tape

More than likely you can unscrew this section of duct work and remove it instead of cutting holes. With it removed, you can either fix the damper or replace the section with a new damper. If the damper itself is fine, the problem may be a clog in the duct itself which is easier to clean with the duct opened up. I've used the dryer vent cleaning brushes from Gardus which would work well for this job:

lint cleaning kit

When reassembling, use self taping sheet metal screws to attach the ducts, and then cover the seams with the foil tape.

  • Thank you for the response! I just tried opening the vent, but it looks like I have tabs that wrap the corners of the duct. When I pry the tab loose (done with hand) it doesn't seem to make anything happen. Any ideas if I don't have screws, and just these tabs?
    – Benny
    Dec 9, 2011 at 2:26
  • @Benny Make sure you got the ears on all sides, then there may be some mastic in there since I don't see any tape. You might have luck sliding a putty knife in the joint to pry them apart slightly to break any seals.
    – BMitch
    Dec 9, 2011 at 3:31
  • please see my update.
    – Benny
    Dec 10, 2011 at 15:26

If it is a manual damper, there is usually a wing nut that attaches the handle to the shaft of the damper. If this wing nut is loose, it might allow the handle to turn without actually turning the internal damper. I would verify that the nut us tight and when you turn the handle, you can actually see the shaft rotating at the same time. If the tube of the duct has somehow been compressed, then the damper would bind up and not work properly.

enter image description here

  • Worth a try, but I think the wing nut is just there for adding tension to the damper (so it doesn't move in the breeze). The bolt itself should have two flat sides that the lever binds too. The key is to be sure the bolt is turning with the lever.
    – BMitch
    Dec 9, 2011 at 3:11
  • 1
    Thank you for the suggestion, but no luck. I made sure the bolt was actually turning, but still same result, no hot air.
    – Benny
    Dec 9, 2011 at 3:44

One other thing to check. In your diagram, the "cold" part is on the left, and you've verified that the damper is not the cause of the problem.

You'll need to check to see what's further to the left of your diagram - air needs an outlet in order to flow, and from your description it doesn't sound like that's happening.

I'd find the first vent attached to the left hand leg, and work back from there to see if something is blocking the airflow. It doesn't sound like there are leaks, because then the left leg would at least be a bit warm.


If the valve to the left is working properly, I think you are going to have to remove some of the exposed ductwork and see what the problem is.

I can suggest snaking a camera through the duct work first before cutting lots of holes everywhere.

There was a home improvement show with the same exact problem as you are having and it was a combination of lack of insulation and faulty ductwork. In fact, in several places, there were very large holes in the duct work as it ran through the walls!

Basically, it was not installed properly so no or very little air was reaching its intended destination.

If this were me, I would hire a reputable HVAC professional to come out and diagnose the problem and look at your heating and cooling system.

  • Great point. We once bought a newly constructed house and discovered no heat in an upstairs room. It turned out that the duct was disconnected inside a soffit in the kitchen ceiling... luckily, I had photos taken just before the sheet rock went up, so it turned out that the first cut in the sheet rock was at the right spot.
    – TomG
    Feb 28, 2012 at 4:10

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.