A/C Blower Fan Run Direction FAQs

Is the air handler fan motor running backwards?
Is the air handler fan installed backwards?

Air Handler Blower Unit Fan Runs Backwards FAQs

How can you tell if the blower fan is running in reverse?

How do you tell if your fan is in "reverse" mode in a beach box on the Island, OBX On 2017-12-17 by Thomas

by (mod) -

Thomas

Though I don't understand what"a beach box on the island" is, nor what island, (Perhaps the Outer Banks of the U.S. state of North Carolina ?),
still I can offer that

if the fan in an air handler is running backwards you would

1. observe that air is not coming out of supply registers in the home but rather going into them. Hold a tissue in front of a register and see if it moves
towards (in) or away from (out) the register.

2. a service technician, opening the air handler blower compartment can observe the squirrel cage blower fan rotation direction and compare that to the angle of the fan blades.

If the fan is rotating backwards it will move very little air and the biting outer edge of the blades on the round fan assembly will be rotating such that they are not biting into air but rather rolling away from it.

More diagnostic and repair details are

at ELECTRIC MOTOR RUN DIRECTION 

New HVAC Blower motor blows air out the return vent and sucks the air in though registers.

Blower motor blows air out the return vent and sucks the air in though registers. What's the problem? It's a NEW package unit. On 2018-10-22 by Scooter

On 2018-10-22 by (mod) - A backwards running blower motor

Scoot,

if we assume that your ductwork is connected correctly then either your blower is installed backwards which can happen during cleaning or assembly, or the motor is running backwards. If a blower motor is running backwards the squirrel cage fan won't move as much air as normal but it will move some.

A backwards running blower motor can be caused by incorrect dip switch settings, incorrect wiring, or even a power surge or lightning strike. Also if you search this website for

electric motor runs backwards

you will find more details

Why is Air flowing backwards in our duct system?

Filter replaced blower motor replaced sucking air not blowing air? - On 2020-09-06 by Kathy

Reply by (mod) - fan is backwards

I suspect that either the motor was mis-wired or the fan was installed backwards.

New blower fan is now drawing air in instead of blowing air out of our ductwork

Just replaced blower fan now it’s sucking air in instead of blowing it out? - On 2020-09-06 by Kathy

Reply by (mod) - look out for blower fan installed backwards or wired to run in wrong direction

I suspect that we have one of these possible mistakes, Kathy:

1. Wiring error:

Most likely: the fan is mis-wired and its driving motor is actually running backwards

2. Wrong fan motor:

The wrong motor was purchased and even wired-correctly, spins in the wrong direction for your air handler. The good news is that many electric motors can be made to reverse direction by a simple wiring change.

3. Fan itself is backwards:

The squirrell cage fan itself could have been installed backwards - it's an easy mistake and the result is it'll move almost no air. If the fan blades are facing the wrong way air flow will be weak and could reverse direction

Our Carrier air handler blower motor runs backwards

1986 carrier blower motor wants to spin in wrong direction On 2016-12-08 by Rob

by (mod) re: blower fan runs in wrong direction

Rob:

Yep that happens, usually after electrical component damage.

See ELECTRIC MOTOR RUN DIRECTION for details.

Rheem Air handler blower fan run direction keeps switch backward & forward

Hi I have a Rheem air conditioner 2014 year. The air handler comes on and then immediately stops and goes back and forth each direction everything seems to be working except fan it does the same when put on just fan on any help would be appreciated On 2019-02-16 by Dave

by (mod) - Air handler blower fan runs backwards - causes, effects

A fan that is reversing and running backwards can be caused by a power surge that damages a control board or relay or on occasion even the motor itself.

On systems that require cooling by a fan such as the outdoor condenser unit, a backwards-running fan will also permit overheating - the system may shut down on thermal overload.

On indoor air handlers a backwards running fan or a squirrel cage blower that's mounted backwards will mean weak air flow through the duct system.

More details are at ELECTRIC MOTOR RUN DIRECTION - backwards

Also see BLOWER FAN ASSEMBLY CLEANING  where we warn about installing a blower fan with the blades facing in the wrong direction.

by Dave

It doesn’t run backwards but 1/4 turn then goes other direction and keeps doing that never spinning I did replace board with exact same one no different

by (mod) -

Usually that sort of run direction problem is explained in the electric motor run direction article I cited above. You replaced the control board but the motor may have a bad start capacitor or damaged winding.

Possibly the fan is mis-wired or a dip switch set incorrectly but I'd belooking first for a loose wiring connection or control board connector or even a bad control board fan circuit or contactor/relay.

Also you'll see in the article problems with run direction related to a bad start/run capacitor.

by Eric W

Dan, I’ll check what you said. The thing that is baffling is why it turns on when a length of wire is attached to just the red wire and the other end isn’t connected to anything.

It’s not completing the circuit so it can’t be shorting out on anything and when that length is disconnected the fan won’t turn on.

by (mod) - fan runs with control wires disconnected

That's crazy. We must be missing something. What the heck? Electromagnetic fields?

More likely you are wiggling something on a control, connector, or board;