Why HVAC Not Working?

You certainly wouldn’t want your HVAC system to let you down on a day when you need it the most. Unfortunately, there are quite a few things that can make your heating and cooling system stop operating.

Why HVAC not working? Issues with the thermostat, a turned-off switch, a tripped breaker, a blown fuse, and a dirty filter might be to blame, as well as the malfunction of one of the system’s components (the control board or blower, for example).

What Would Cause HVAC Not to Work?

Issues with the thermostat

The first thing that you should always do is check whether your thermostat has the right settings. It should be set either to ‘heat’ or ‘cool’.

Make sure that the device is on, that it has fresh batteries, and that it is located in a place where it can make correct readings (out of the sunlight, away from heat sources).

One of the switches is off

The good news is that in a lot of cases your HVAC equipment is not working simply because someone might have accidentally bumped the switch.

There might be a few switches (both indoors and outdoors), so make sure to change all of them to ‘on’.

A tripped circuit breaker

A short circuit or an overload will make the breaker trip. Don’t forget to flip it back, before switching your heating and cooling system on.

A blown fuse

In an HVAC system, you can locate the fuses in the disconnection box. The fuses protect the components from overheating.

A power shortage, an overload, or the malfunctioning of a component can blow one of the fuses. This is done to prevent more serious damage.

A clogged filter

If you don’t regularly change your system’s filters, they will get dirty and will, eventually, restrict the airflow.

Without enough air, an AC unit can freeze up, while a furnace might not be able to fire up. A clogged filter can also cause the system to overheat and break down.

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Mechanical issues

Any of the components of your HVAC system can experience a malfunction. The unit might not be able to work at all without a properly operating blower, control board, etc.

Read: HVAC Thermostat Problems

What to Do If HVAC Is Not Working?

There are a few relatively easy things that you can do on your own to try and make your heating and cooling system work.

Check the thermostat

The device should not be set to ‘fan’. If you want the temperature in the house to change, then choose either ‘heat’ or ‘cool’.

Make sure that the temperature setting is correct and test if the thermostat is able to read the room’s temperature correctly.

To do that, place a regular thermometer on a piece of paper and tape it to the wall; compare the readings in about 15 minutes (a 3-degree variance is acceptable).

Inspect the outdoor unit

Your AC has a condenser, a furnace might have a flue. Check these outside parts of your system and make sure that they are not clogged.

Always try to keep the space around the unit clear.

Change the filter

Your HVAC system might have a few filters. 

The furnace’s filter is located in the blower compartment. If you have an air handler, it would have a filter as well.

Finally, practically every return vent will have a filter behind it.

Make sure to check all the filters once a month and replace them as soon as they get dirty.

Inspect the air registers

You would have to make sure that all the registers are fully open. Move the furniture away from the vents.

Also, it is not recommended to close the vents even in the rooms that you are not using. This will restrict the airflow and make your system work harder, so always leave all the vents in the house open.

Read: Why HVAC Is Important

How Do I Reset My HVAC System?

You might want to first try to reset your thermostat.

Simply push the reset button and hold it for at least 5 seconds, shut off the breaker to the device for around half a minute, or put the battery backward for a few seconds.

To reset your gas furnace, you should:

  1. Turn down the thermostat setting and turn off the power supply to the unit.
  2. Turn off the main gas supply (leave the pilot gas supply turned on).
  3. Relight the pilot with a match.
  4. Turn the power supply on and after that – the main gas supply.
  5. Raise the thermostat’s temperature.

To reset an electric furnace, turn off the power supply and press the reset button (it’s usually in the blower compartment).

Read: Why Does My HVAC Keep Blowing Fuses?

Where Is the AC Reset Button?

You might find the button on the outdoor unit. Usually, it’s located along the bottom edge.

The reset button might also be somewhere inside the indoor unit. Look for it behind the service panel, but don’t forget to switch the power off.

Read: Does HVAC Use Gas?

Why Is There No Air Coming From Vents in My House?

The damper is closed

Some vents have a toggle or a switch that closes and opens the damper inside the vent. Make sure that it stays open.

A dirty air filter

Replace the filter regularly

An underpowered unit

If there is no air coming from a vent that is farthest from the heating or cooling unit, then it might be too small for your house.

Dirty ducts

There can be an obstruction in the ductwork.

Leaky ducts

The vents might not have any air coming from them if the ducts are leaky and/or disconnected.

Read: Quietest HVAC System

How Do You Test HVAC Vents?

The simplest test involves a tissue.

Dangle the piece of tissue around 6 inches away from the return duct – the paper should be clinging towards the vent.

Then place the tissue right against the return vent – the airflow should be strong enough to hold the piece of paper in place. If the tissue is sliding or falling off, then you have a blockage or a leakage somewhere in the system.

How Do You Check for Clogged Air Ducts?

The most common symptoms of clogged ducts include:

  • A difference in temperatures throughout the house
  • Increased utility bills
  • Poor indoor air quality

To check the system for clogged air ducts, turn it on and wait for the fan to start. Inspect all the vents in your house and mark the ones that are blowing/sucking less intensely or are not blowing/sucking at all.

Inspect the vents in the rooms with less airflow. Remove the filters, unscrew the covers, and use a flashlight to check right behind the grille for debris or any obstructions.

Leave the rest to a professional.

Why Home Air Conditioner Stops Working After a Few Minutes?

  1. Your thermostat is located in a ‘bad’ place – don’t install the device near a window, a supply vent, or an exterior door.
  2. The filter is dirty – a clogged air filter can make the coil freeze up which will cause the system to turn off.
  3. A refrigerant leak
  4. Your unit is oversized – such air cons will cool your house too quickly.

Failing parts – one of the internal components might be failing (like the run capacitor or compressor, for example).