Why HVAC Zone Damper Not Working? Troubleshooting Guide

If an HVAC zone damper is not functioning correctly, then you won’t be able to enjoy the benefits that your zoned system has to offer.

A zone damper can stop working, if it gets stuck due to dirt accumulation or if the damper motor or the damper’s spring had gone bad. In automatic dampers, power issues and problems with the wiring might also be to blame. 

Why HVAC Zone Damper Not Working? 

There are quite a few things that can make your zone dampers stop working.

  • The damper can get stuck because of the accumulation of dirt around it or due to an obstruction
  • The damper will stop working if its motor had gone bad
  • Automatic dampers should be able to respond to the thermostat’s commands. If there is a wiring issue between these elements, the damper will not work
  • Automatic dampers might also stop operating if there is a power issue (a lot of dampers are powered close)
  • If your dampers have a spring, then this part might go bad over time

Read: What Are Zoned HVAC Systems?

How Do You Troubleshoot Zone Dampers?

  • The first thing that you should do is determine whether you have manual or automatic dampers. It’s fairly easy to do that – look for a handle on the side of the ductwork (only manual dampers will have one).
  • Follow the ducts from your dampers to the corresponding register – you might want to work with a partner as one of you would have to turn the system on, while the other would be checking the airflow.
  • If you have a manual damper, adjust the handle and close it. Check the airflow through the register – if there is air flowing through the register when the damper is closed, then it looks like the element had gone bad.
  • With an automatic damper, simply turn the HVAC system on and check the airflow. The ‘symptoms’ of faulty dampers include insufficient airflow or too much airflow.

How Do You Troubleshoot a Honeywell Zone Damper?

  1. If you have a new HVAC system, then ensure that there are no screws attached in the wrong places (they might be ‘holding’ the damper).
  2. If your system is over 8 years of age, then the spring might have gone bad. 
  3. Try to manually push your Honeywell zone damper open. If that’s the only way you can get the element to open, then the damper motor is to blame. 

How to Adjust Automatic Dampers?

Typically, when the HVAC unit is powered, the motor will rotate the damper until a certain position is reached. Once the power gets removed, a spring pulls the damper into its regular position.

In adjustable automatic dampers, you can change the plate position (detach the spring, loosen the screw, and rotate the plate to the intended position). In such a case, the damper will become either less closed or less open.

Read: Why Dual Zone AC Not Working In One Zone? Troubleshooting Guide

Bypass Dampers Problems

A bypass damper is, basically, a pressure relief valve that is placed between the supply and return ducts. Once the zone dampers start closing, the bypass damper will open up, allowing some air to pass through it.

The main problem with bypass dampers is that when they are open, the strength of the airflow in the system drops. This might cause:

  • A higher inlet temperature
  • An evaporator coil running colder (this means possible freezing issues)
  • Duct sweating issues

Read: What Are Zoned HVAC System Problems?

How to Manually Open a Motorized Damper?

Check the motor’s manual. Some of those have a manual release button, and if that’s your case, all you would have to do is push the button and turn the shaft by hand.

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Motorized Damper Stuck Closed

It might be extremely challenging even for an experienced DIYer to figure out what’s wrong with a motorized damper. Ideally, you would want to call an expert as such issues usually mean that the damper had gone bad. 

Read: Does HVAC Zoning Really Save Money?

How Do I Fix My HVAC Damper?

Locate the damper in the HVAC system, open up the ductwork, and remove the element. The chances are high that you would have to replace the damper with a new one. 

How Do You Fix a Stuck Damper?

If the damper is stuck closed, then the problem is with the motor or there is a power issue.

If the damper is stuck open, then you should:

  1. Disconnect the damper from the motor and the damper crank arm to check, if the element automatically closes.
  2. Make sure that the damper is moving freely.
  3. Power and then remove the power from the motor to find out if any of these actions will make the damper work.

Read: How Well Do Duct Boosters Work?

How Do You Fix a Broken Damper?

Changing the damper motor might solve the problem, but in the majority of cases, you would have to replace the whole element. 

How Do You Test a Vent Damper?

Turn off your HVAC system and turn the fan setting to ‘on’. Inspect the associated zone for airflow.

If you have minimal airflow or the room feels drafty, then you might have a defective damper.

How Do You Tell If a Zone Damper Is Open or Closed?

If you’re not able to visually inspect the damper and you’re not planning on removing the whole thing from its housing, then you can simply turn on your HVAC system in all the zones. If the air is flowing through all the registers, then the dampers are open.

By the way, some dampers have a colored indicator that shows whether the element is open or closed. A green switch would mean that the damper is open, while a red one – that it’s closed.

How Does a Zone Damper Work?

Manual dampers usually have a lever outside the ducts and air vents, so that you can easily adjust them.

Automatic dampers are considered to be more user-friendly as they don’t require any action on your part. These elements come with small motors that control the shutting and opening of the plates and valve.


How Long Do Zone Dampers Last?

With proper maintenance, zone dampers can last for 15-20 years.

How Do I Know If My Damper Motor Is Bad?

The signs of a faulty damper motor include:

  • Abnormal or inconsistent temperatures throughout the house
  • An HVAC system that is struggling to maintain the chosen temperature
  • Limited airflow in the rooms

How Much Does Damper Replacement Cost?

The cost of a new motorized damper can range from around $100 to $200 and be prepared to pay for professional installation an additional $150-$250.

Where Are HVAC Dampers Located?

HVAC dampers can be typically found in the main supply trunks. Those are the parts of the ductwork that are blowing cold or warm air (depending on the season).

Some dampers can also be located after the major junctions.

How Many Types of Dampers Are There in HVAC?

Dampers can be classified not only as ‘manual’ and ‘automatic’ – there are also plenty of other types of dampers that can be used in a heating and cooling system.

  • Multi-zone dampers usually have multiple actuators (each controlling a separate zone)
  • Backdraft dampers restrict airflow in one direction with the help of shafts installed on one end of the blades
  • Control dampers simply regulate the airflow through the system (they can also be used in air mixing zones)

Balancing dampers are responsible for regulating the air pressure in the rooms that are connected to the ductwork