HVAC blower fan testing & diagnostic questions & answers:

Reader questions & responses help diagnose trouble with the blower fan or air handler fan used in both air conditioning and heating systems.

This article series discusses how to inspect and test a heating or air conditioning indoor air handler blower fan that is not working. We also discuss convector unit fans and we suggest diagnostic steps for squirrel cage blower fan squeaks and noises.

Heating or Air Conditioner / Heat Pump Blower Fan Testing & Diagnostic Procedures Q&A-4

The questions and answers discussed below were posted originally at BLOWER FAN OPERATION & TESTING - please be sure to read that collection of diagnosis and repair steps.

The blower fan is located inside either a vertical or a horizontal air conditioning unit in many home air conditioning and heating systems.

Click to enlarge any image]

On 2020-05-13 1 - by (mod) - check that the air handler unit has electrical power

I can give some steps in checking for power, but beware that if you're not trained in safe electrical wiring and testing you could be shocked or killed, as fooling with wiring and connectors is dangerous.

First find the brand and model of your heater, if you don't have one, we find the service manual for it, and we find the RESET button or control that trips off when a burner is inoperative. Those are different for gas vs oil and can be in different locations. I don't know enough about what you've got to be more specific.

Next we find the power switch that turns power to your heater on and off - usually on or close to the heater.

Then with power OFF at the panel we use a voltage tester to confirm that power is off at the heater switch, then turn power on and test again for power at the heater. If you don't have a voltage detector or tester it may be possible to use a light fixture.

On 2020-05-13 by Stephen

Everything else in the basement has power. The furnace could lose it, how could i tell? What other options are there? Out of work and really can't afford a tech to come in

On 2020-05-13 - by (mod) -

Or power is lost

On 2020-05-13 by Stephen

The Honeywell Continuous Retry LED unit does not light up. The temp in the house is lower than the setting at the thermostat so, I would think, either the heat should be on or the LED should flashing, no?

On 2020-05-13 - by (mod) -

Does the unit have electrical power?

On 2020-05-12 by Stephen

Ok, tried jumping it and still nothing. Time for a new blower control panel?

On 2020-05-12 by Stephen

It is gas fueled

On 2020-05-12 - by (mod) -

Disconnect the thermostat wires at the heater

Jumper wire the two thermostat terminsls at the heater

If the burner does not stsrt the probkem is there.

Ix it oil or gas fueled?

On 2020-05-12 by Stephen

The burner isn't turning on and the blower doesn't start. When the thermostat reaches the temp that the heat should go on, you can hear the "click" in the thermostat that would turn it on but, the furnace never fires up or tries blowing anything.

On 2020-05-11 - by (mod) - orderly sequence of diagnostic steps for the no-heat problem.

Possibly, Stephen, but let's take an orderly sequence of diagnostic steps for the no-heat problem.

Start at https://inspectapedia.com/heat/Furnace-Diagnosis-Repair.php FURNACE DIAGNOSIS & REPAIR

and let me know what you see, find, think, or want to ask about.

You'll need to actually look at your furnace, first to see if the burner is turning on or not, and second to see if the blower starts or not. On a furnace system the blower won't start until the heater's burner (*gas, oil or what?) heats up the heat exchanger and air plenum,

On 2020-05-11 by Stephen

I woke up yesterday and my wife was complaining how cold it was in the house. We have the heat set to come on at 65 and it was 59 in the house but the heat wasn't coming on. I adjusted the temp and could hear the thermostat clicking to turn it on and off but....no heat.

I bought and installed a new thermostat and it does the same thing. You can hear it cycle as if turning the heat on and the display shows :heat on" but, again, no heat. Could it be the blower control panel?

On 2020-01-07 by Anonymous

In the ARTICLE INDEX you'll see articles on FAN CYCLES DURING HEAT and FAN CYCLES AFTER HEAT STOPS (those are approximately the titles) where you'll find useful diagnostics for the case you describe

On 2020-01-07 by Anonymous

@Steve, So could you tell me what control the blower to cool down the heat exchanger temperature? I suspect my furnace problem is: heat exchanger not cool enough, but blower stop. When sensing again the plenum temperature too high it starts again, but stop after a few seconds until the next heat cycle.

Can I change the temperature lower, to stop blower? I already changed the LIMIT switch. This is open at 250 C and close 210 C. Is it available wider range limit switch?
Thanks.

On 2020-01-03 - by (mod) -

Steve

Let's start with the diagnostics at FURNACE FAN CYCLES AFTER HEAT

On 2020-01-03 by Steve Varadi

We have a gas furnace HVAC. Everything is working fine except when heat call satisfied (stop heating) a few second lather the BLOWER fan start again for a few seconds. Sometimes this repeat again before finally stop for the next cycle.

At first I changed the control board, later the Limit switch was replaced. BTW. I checked the Limit switch with ohmmeter, it is normally closed. As I see open 250 close 210.
What should caused this repeated blower start?? (No spark, no gas open, only the blower start for a few seconds). Otherwise everything is normal operation.
Thanks.

On 2019-11-19 6 - by (mod) -

Thanks for the question, Steve.

Take a look at

BLOWER FAN SPEED SETTINGS

where we give fan speeds in CFM for typical situations.

Then take a look at the diagnostics and solutions at AIR FLOW TOO WEAK https://inspectapedia.com/aircond/Weak_Air_Flow.php

On 2019-11-18 1 by Steve

How fast (cfm) should the blower fan (york ZF240N) be with a outdoor temperature of 45 degrees? Doesn't seem to be moving much air.

Reader Question: HVAC blower acts crazy, seems to be trying to cool and heat at the same time

(July 6, 2011) Zack  said:

Ok, hopefully someone can help me here, my blower isnt working, which is no big deal to replace, but my whole unit is acting crazy, its calling for heat and air at the same time?

Could that be due to the blower motor not working???

Reply:

Sounds like a control board circuit problem; check the thermostat settings and if they look right you need a service call.

Reader follow-up:

I have someone coming to look at it tomorrow, but when I talked to him, he said that it is possible that the motor being bad could cause that, I don't see how but I was just wondering if its possible? - Zack

Reply:

Zack, certainly no one of us knows all about anything. But I don't understand how a bad blower motor would call for heat and air at the same time. A bad blower motor ought to mean that air stops being blown through the ductwork. The absence of cooled air would be sensed by the thermostat set in cooling mode and the TT would never be satisfied - it would keep calling for cooling. (When a blower stops the coil may ice up, further stopping air movement). I don't see how that would call for the system to switch to heating mode. Is the service tech arguing that your system switches to heating mode because it's detecting an iced cooling coil? Let us know. What you're told will surely help other readers.

Reader Question: A/C runs more and more often and I smell burning

(July 26, 2011) Mark  said:

My A/C unit is kicking on and on more frequently and smells like something is burning up. House maintains temp

Reply:

Watch out: Mark: if you smell something burning at electrically powered equipment I'd turn it off immediately and hire a qualified technician to investigate the problem. The risk is that the overheating is ignored and you have an electrical fire.

Reader Question: Central Air Blower fan gets hot and stops

(July 29, 2011) Barbara  said:

my central air unit is outside...it is 30 years old...the fan gets hot and stops...after it cools down it will start up again..had new fan installed and it does the same thing...the fan just hums after about 10 mins of cooling...where do I start or should I just look for new unit?

Reply:

Barbara it's odd that a new fan motor would overheat and stop running unless
- the temperature is actually within normal operating range and it's a start/run capacitor that's failing
- there is a wiring or other problem causing abnormal overheating.

Are you sure it's just the fan motor and not the compressor that's overheating?

Reader Question: A/C doesn't work right, poor cooling - ducts too small?

(July 31, 2011) David W. Hesson  said:

I have a real problem. I bought a new heat pump about 4 years ago and the a/c portion doesn't work the way it is supposed to. It might be, say 74 degrees in the house and then I move the thermostat to 72 degrees, The temperature in the house goes to 75 degrees and stays there.

But sometimes if I only move the thermostat 1 degrees the a/c might cool the house down 1 degree. This has been this way since we bought it Dealer has been out here 6 or 8 times. He always finds something wrong. Too much freon, not enough, wire off thermostat etc.

The one mechanic who appears to have the most sense say our air return duct is too small and we need a bigger one. They offered to put one in for $200. I say it should have been fixed when unit was installed. Plus no other visit has fixed it. We live in Virginia. This has really been frustrating. Please help

Reply:

David those explanations about A/C troubles leave me confused.

If the air coming out of your supply registers is not cool the system is not working and it's more than a duct problem.

Take a look at the article titled DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP - that you can find on this page at Continue reading where you will find an ARTICLE INDEX to RELATED ARTICLES that includes a live link - for some suggestions that might get us on track, and ask for an experienced, senior, trained HVAC tecnician

If there is no air coming out of the supply registers that's often a fan or filter or duct problem, or a cooling coil blocked by ice.

Question: Fan Motor Failed, Froze Coil, Repaired, Now Blower fan & AC work only if fan is set to FAN ON, does not work in FAN AUTO position

My parent's furnace fan stopped working while they had their A/C running. It resulted in freezing up the A-coil and a wet mess. They still have their original Honeywell T89F Zone Thermostat.

With the thermostat set to "COOL" and as long as you have the thermostat set to "FAN ON"... the A/C will work and regulate temperature properly. But as soon as you move the switch over to the "AUTO" setting, the furnace blower motor stops and the outdoor unit still runs regardless of how low a temperature setting.

Manually operation the A/C is a bit of a complicated chore for a couple of 90 year old parents. Can you give some pointers to help them out? - B.C. Ohio, 7.21.2014

Reply:

I take it that the fan was repaired after it stopped working.

It seems unlikely to me that a fan failure would have damaged the thermostat itself - and as you are confident it was working properly previously with FAN AUTO set then

I infer that the thermostat re-wiring to drive the fan was not properly done.

So I'd start by calling back the repairman to fix the mis-wiring.

Meanwhile you could simply leave the fan on 24/7 in the FAN ON position. That will result in more even house temperatures and improved air filtration at a little increase in electricity cost.

The thermostat should still turn the A/C cooling system on and off in response to temperature.

Try that and keep me posted. - DF

Question:

(Aug 20, 2011) Steve said:

When I turn our central AC unit off the blower stops, but I hear a noise like another fan or blower keeps running.

(Sept 5, 2011) Cindy said:

We have been experiencing intermittent delays in the blower motor coming on after the compressor starts. We have had two repairmen out to look at the system. The first could find nothing wrong and told us to call back if the blower motor does not come on at all because if that happens the coils could freeze up and the whole system would go out. The second repairman cleaned the compressor again, which is something my husband does regularly anyway, and added two pounds of freon. This has still not solved the problem. It seems to us that this behavior should be an early indicator that something isn't right within the system. I am looking for a suggestion as to what might really be wrong with our air conditioner.

(Sept 20, 2011) Wesley Erickson said:

my air handler fan keeps running. someone told me it could be the contact switch stuck. is this a easy fix ?

(Dec 4, 2011) Bob said:

When My Weil Mclane boiler blower shuts down after reacing thermostat temp, the boiler unit shakes. the blower motor seems fine with no noise....... is it the blower unit or the motor with a work shaft? how to check? boiler is22 yrs old.

(Apr 27, 2012) Diane said:

It rained every heavily and the fan or motor sounded like it was having a hard time kicking in. I turned it off for several days thinking that it was wet and needed to drt out. It still does not blow or heat. It is a dual window unit. Heater/Air Conditioner. Whay should I do before calling a repairman?

(July 18, 2012) Paul Galante said:

The blower isn't vibrating it just that the blower makes a lot of noise

Reply:

Paul,

It may be useful to track down just where the noise is originating, more precisely - to a motor, a loose mount, a rattling duct, etc.

Question:

(July 19, 2012) george said:

we came home from a trip. before coming in double wide mobile home i was wattering my dog. i saw ice on outside unit line going into home, wife said insde coile were frozen badly, i came in and it was. i saw squrile fan was turning, but slow. i turned it of an spunn the fan and it spun easy and fast, after turning it back om it was still really slow, so i took off bottom cover where breakers are and turned em on an off , fan still slow, after doing this several times i saw electricle sparks on left side of fan motor. turned it off an on , it sizzeled then stoped , but fan still ran @ slow rpm. please tell me what you think.

(Aug 6, 2012) Anonymous said:

Sticker says the control board has been integrated with the blower motor.
Do i need to remove the entire motor now?

Reply:

Anon,
Will the blower stay on if you set the thermostat switch to
Fan on or manual?

If so take the thermostat out of the circuit and then check for a loose wire, sensor, or control board or relay

Question:

(Aug 21, 2012) Eric ...eric.rodney@doe.state.nj said:

When either the furnace or air condistioner are on the noise level from the blower is extremely loud overpowering conversation. Is there anything that can be done? Is the location of the furnace, proximity to the register and afdjoining room a factor? help.

(Aug 22, 2012) Nancy said:

I just replaced the fan motor and capacitor on my condensing unit but haven't turned it on yet because someone told me to make sure there is only 1/4 " between the bottom of the motor and the fan blades (stating it will perform best) and that I should break off the screw ends to accommodate this. I have it placed about halfway down the rod coming out of it that the set screw tightened to, which seemed a safe distance for the blades to spin. Please advise if this will help or hinder my operation.

(Sept 4, 2012) Chris Lent said:

I am changing my blower motor and I can't get the old one off(shaft is stuck, motor won't slide out...I already did a no-no by using as a hammer to try and force it out...someone told me I needed to use a crescent wrench and give it a turn and it should slide out easily..? I don't see how I can get a crescent wrench into the space the assembly allows?

(Oct 11, 2012) Debbie said:

I have a central heater that the blower won't come on. However, if you turn on the A/C part, it works! What is happening?

(Oct 29, 2012) Brandan said:

I have just recently hooked up a new thermostat on my unit. My unit is a American standard runs off of propane. How do I now if it is a heat pump or the heat pump was never hooked up and it's just running like a furnace. I have is set on reg. not heat pump. It heats. When I turn it to heat pump the fan turns on which does not turn on when it's on reg. when on the burner light and the flame shoots down the tubes and all other burnt gasses go out the top. Then the unit kicks on and heats the house. The only reason why I think it is a heat pump is because the propane line Hans a union and seems like it goes somewhere els? Is it a heat pump or it's just not hooked up for it?

(Nov 6, 2012) david said:

my heater fan pops on and wont cut off blowing cold air. I have to throw the circit breaker to cut it off. Even then when I cut breaker back on fan starts running again? So I cant use my heater

(Nov 15, 2012) Bryant 355AAV Blower to high spe said:

I have an older home converted to forced air. The old fixed capacity furnace pushed air to the second floor better than my new variable volume blower. I have the Bryant Evolution thermostat fan setting on high but it sure does not run on high very often. It still runs low and medium and goes to high if not satisfied in a certain time. Meanwhile I am not pushing air to the upper floor. Can this thermostat be programmed differently? or can I buy a simpler thermostat that will drive the fan to high speed?

(Dec 27, 2012) Rodney said:

About a year ago we had our Air handler replaced in the attic with a new one because we had mold blowing out our vents. Now all of a suddened it stopped working and i found a wire melted in half where it was connected inside the unit in the attic. What would cause that and what should i check before connecting the 2 wires back together. No breakers was tripped.

(Feb 3, 2014) Anonymous said:

fan on outside unit works. fan in heat exchanger does not work. What to lok for.

(Feb 4, 2014) Rick said:

My heater and blower work, but when the heating cycle shuts off the fan keeps blowing cool air, have to turn the thermostat down to get it to shut off, I can't find anything on the internet that discusses this type of problem, anybody have any recommendations?

Reply:

Sure, Rick. Thanks for asking. We have an article on how to diagnose and fix forced warm air heat when the furnace fan won't stop when it should. Just search InspectApedia for

Furnace or A/C Blower Fan Won't Stop Running

and you will find a link to the article.

I will also add this topic and the necessary link on this page.

Question:

(Apr 3, 2014) Anonymous said:

I have a day & night hvac unit. The blower comes on when ever it feels like and blows for a couple of minutes then shuts off. I've disconnected the thermostat that didn't work. What do I do now?

Reply:

Sounds like a bad blower fan switch, relay, or limit switch. But before replacing any parts, disconnect the thermostat wires at their other end - rather than at the thermostat. That will eliminate calling for heat (or cool) by a short between the wires.

Question: Coleman oil fired furnace blower troubles

(Apr 8, 2014) Anonymous said:

I have a new coleman oil fired furness the burner runs fine but the blower motor starts and stops this unit is made by alpine

Reply:

Anon I can't quite make out the question - if you mean the blower starts and stops rapidly intermittently when you think it should not, that suggests a bad fan limit switch or a bad thermostat or thermostat wire.

Usually on a call for heat the furnace will heat up, then the blower turns on, and the blower and furnace will continue to run until the call for heat is satisfied at the thermostat. Then the thermostat turns off the burner; the blower will continue to run until the blower assembly has cooled down, then it stops as well.

Check the fan limit switch operation;

Check for a dirty filter causing the plenum to overheat

Check for a dirty blower fan causing the same problem by moving too little air

Question: wobbling blower fan noise - rattling

(May 10, 2014) Anonymous said:

when my air conditioner shuts off it makes a terrible noise. it sounds like the squirrel cage is rattling. what could cause this?

Reply:

Anon,

I'd ask for a check by the HVAC service company. If there is excess refigerant entering the compressor it can make a rattling noise and can destroy that expeensive component. If the problem is a loos fan itself that's easy to diagnose by checking the fan assembly with power off. The fan should not wobble.

Question: Gibson gas furnace lost blower speed

(May 22, 2014) Anonymous said:

I have a Gibson kg6rc 100c-16b natural gas furnace that SUDDENLY lost RPM of blower assy and cold air stream droped dramaticaly though there is SOME stream, so fan wheel is rotating and clean. I checked it.
HELP!

Reply:

Assuming this is a direct drive unit not a belt driven fan I'd look for a failed motor, bearing, or start capacitor.

Question: blower shuts off after 30 seconds

(May 23, 2014) BErik said:

Blower Motor shuts off after 60 seconds:
I have an older Trane gas furnace / central AC unit. Cleaned the AC coils (outside) yesterday and turn on AC today. Started fine, but after 60 second, blower (inside) shut off, but outside unit continued to run.
Trouble shooting:
Turned Fan ON at thermostat - fan/blower ran 60 seconds, then shut off
Jumpered Fan ON (thermostate wires R to G) - fan ran 60 seconds, then shut off
Turned on AC - outside unit and fan came on, but fan shut off after 60 seconds, outside unit ran
Turned on Heat - heat functions worked normally...burner heats, fan on, at temp burner off, fan off after delay.

Any suggestions on what is shutting down the fan after 60 seconds?

Reply:

Berik, if you are in heating mode watch the fan limit control switch. If the heater is shutting off at the upper safety limit then air flow is probably blocked, causing overheating.

If you are in cooling mode I wonder if your system has emergenc heaters running.

(May 23, 2014) BErick said:

Looked at this some more. New blower motor replaced in the winter works fine in Med-High speed, but for A/C and Fan-ON motor is on HIGH and seems to be shutting down...I assume on over-temp. Air flow seems good, over temp shut down even when panels off the furnace. I will look at wiring, voltage next.

(mod) said:

Good progress. If you can safely measure current draw that'd be helpful.

(May 23, 2014) BErick said:

I currently have the furnace-side High connected to the blower-motor Med-High wire, like when the heat was on. Operation in the lower speed is working. I was able to measure current draw. The motor is an Emerson M55HXHKP-9722, 115V 14 Amp. Using amp meter, got the following readings: High - 18-20 Amps, Med-High - 14 Amps, Med-Low 10 Amps.

I know the motor should not draw 18A on High, based on its rating. Do you think this means the motor is bad or has failed?
Thanks.

(mod) said:

Yes BE.

Question: motor can't drive fan - overheats

(june 1, 2014) joseph said:

The indoor fan motor is working normal without belt, and i connect the belt to the blower the motor is high amper and become heat, what is the main problem, i also adjust the belt, the alignment, the electrical are okey! Please help

Reply:

Joseph

Possibly the motor is failing under load and drawing high current, or a belt-pulley bearing is jamming.

Question: Inter City HVAC BM1912GSPL4 blower noise

(June 4, 2014) james said:

i have an inter-city hvac system installed when i built my home in 1995. the model (and mfr) number on the sticker is BM1912GSPL4. my problem is, the blower fan (squirrel cage) began making noise a few days ago. i found a tutorial which duplicates the sound perfectly and is consistent with it's otherwise lack of symptoms. eg; no apparent vibration, good airflow, no squeals, chirps, stops and starts without issues, etc. on the tutorial, the culprit is two loose blades on the squirrel cage. the tutorial suggests jbweld to repair the loose blade(s), or replace cage. i would like to replace it, but am unable to locate the part. sears says my model number is not in their database. any suggestions?

Reply:

James,

I'd remove the assembly, take it to your local HVAC supplier, and see if they have a replacement.

Or check for a misread model number.

Keep me posted

Question: Blower fan won't stop running

(June 5, 2014) Drew said:

I have a 1980's Lennox (I am at work right now). AC runs fine, heat runs fine. However when I put Fan setting to ON it shuts off after a few minutes. Outside unit and Main unit - nothing works. And it wont turn back on until after a good 30 minutes or so. It does not do this with the AC on at all. I was previously able to run the "fan on" setting for as long as I wanted. Thanks for your help.

(June 29, 2014) jim said:

Hvac fan runs almost all of the time. I have a carrier thermostat unit appears to be working but?

Reply:

Jim please see the "blower fan won't stop" diagnostic advice at

inspectapedia.com/heat/Furnace_Fan_Wont_Stop.php

and let us know if questions remain

Question: lost cooling, blower gets weak

(July 2, 2014) doug lake said:

i have a self contained a/c unit outside of my double wide.it doesnt seem to cool as good anymore/had it tested..everything ok.do the blowers get week on these after a while-.there is a big fan on the top.-i checked tube under the home seems ok.blower pressure weak in vents-air filter is clean-

Reply:

Check for dirty blower fan blades and also for dirty air filter or air leaks. Also check for low voltage or slow motor

Question: where is the noisy blower sound coming from ?

(July 9, 2014) Chhayhour said:

Somebody know, where is the noisy sound come from? Is coming from the cooled air blower? Or another equipments? I am really boring with its sound so much. I don't know how to fix this issue. please help me to fix it!

Reply:

Chhayhour

You can find air conditioner or HVAC sound diagnosis procedures at

inspectapedia.com/noise_diagnosis/HVAC_Noise_Diagnosis.php

Anon,

If the blower fan motor won't turn ON or is noisy, there may be
a ELECTRIC MOTOR OVERLOAD RESET SWITCH that has tripped off due to thermal overload or an electric motor or voltage problem. Don't forget also to look for other switches that could prevent the air conditioner from even starting, such as a condensate overflow pan sensor switch (
see DRIP TRAY DEFECTS) that can shut down the air conditioning system to avoid damage from overflowing condensate pans.

Question: sparks coming from HVAC blower unit

(July 28, 2014) Anonymous said:

sparks coming from blower

Reply:

Watch out: Anon"

TURN OFF THE SYSTEM immediately as you are risking an electrical fire.

Question: frozen up air handler and refrigerant piping, burned wires,

(July 31, 2014) Bill Morse said:

I have a Goodman ARUF303016AA air handler. The system froze up all the way to the outside compressor. I shut it down and let it thaw. Turned the fan to ON at the thermostat and got nothing. I found the red wire from Transformer 240V, to the Blower time delay relay, burnt off.

I put a new end on it, hooked it back to the relay, and tried it again. It started burning it again, and started melting the side of the relay. Where should I start looking for the cause? The 3 amp fuse on the control board, that the relay is attached to, did not blow.

I have a new relay/board, but would rather locate the reason before burning up another one. Any suggestion would be appreciated.

Reply:

Bill,

When there's a burn-up such as you describe indeed it's essential to diagnose just what component failure is causing the burnup before replacing anyhing. Could be a failed compressor, other motor, relay, control board, etc. I can't offer specific diagnostics from just an e-text, and if it were my system I'd ask for help from an experienced HVAC technician. Keep me posted on what you and the tech find as what we learn will help others.

Aug 25, 2014) Anonymous said:

Dan, Thanks for your input. I have found that with the thermostat set to auto and on cool, There is continuity from red to yellow, green AND White, which tells me the Thermostat is bad. I'm not sure if the blower relay wire burn caused the Thermostat short, or vice versa, but I'll be putting in a new Stat, before trying the new relay.Thanks.

Mod replied:

Bill

OR the TT wires are shorted together.

Disconnect the thermostat from it wires completely and really to be unambiguous, disconnect the wires at the air handler end, then check the wires - there should be no continuity between them. If there is then they shorted enroute; if not the problem is on the thermostat end or the control board end

Question: installing a larger fan to improve air flow

9/11/14 Anonymous said:

Can I install a larger squirrel fan in my HVAC Unit to increase air flow?

Reply:

Unlikely, Anon - as the blower assembly is most likely already physically sized to fit the cabinet.

However depending on your air handler design and ductwork it may be possible to install an dual speed or variable speed blower than can increase air flow.

Before doing so I'd check the various reasons that air flow may be inadequate to be sure that none of those is the real problem.

see weak HVAC system air flow diagnostics at

inspectapedia.com/aircond/Weak_Air_Flow.php

...

Continue reading at BLOWER FAN OPERATION & TESTING or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see BLOWER FAN OPERATION & TESTING FAQs-5 - more-recent Q&A about testing the HVAC blower fan.

Or see these

Recommended Articles

• AIR HANDLER / BLOWER UNITS - home
• BLOWER FAN OPERATION & TESTING

Suggested citation for this web page

BLOWER FAN OPERATION & TESTING FAQs-4 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to AIR CONDITIONING & HEAT PUMPS

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INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING FURNACES

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