Blower motor seems run weak - any suggestions?

jsda77

Hello guys,

I'm a new owner of 30 years old house.
This house's 2nd floor AC system runs weak. I can not feel any air stream from vents.
Previous owner told me that they hired technician to fix issue and problem was low refrigerant but I don't think so.

I changed filter and check / clean evaporator coils and condenser fins.

Are there any other suggestions to fix this issue except just call the pros?

Does bad capacitor slower blower motor?

Sincerely,



Peter

HVACNUT

How old is the system?
This system is for the second floor only, meaning just one thermostat controls it?
You mentioned capacitor, but its definitely not an ECM motor?
Does the motor run at all?
Low refrigerant can cause little to no air flow due to the evaporator coil freezing.

GW

Yes I’d check the cap first, don’t zap yourself

pecmsg

Any # of things can cause the air flow too drop...…..
Plugged Filter
Collapsed ducts
Restricted ducts
Evaporator Frozen
Evaporator dirty
Dirty Squirrel cage
Insulation blocking ducts

You need someone to inspect the unit!

Ironman

If the system previously had a leak that caused the evap to freeze up, that could have caused the blower motor fail.

With the blower turned on and the a/c off, just remove the blower door and see if it's running. If not, the motor, capacitor, fan relay or board could be bad.

Tinman

Measured voltage? Measured amp draw? Capacitor checked? Delta T across coil?

EBEBRATT-Ed

put an amprobe on the motor and check the amp draw compared to the motor name plate. Theck that the motor is turning the right way. Check for leaking disconnected or broken ductwork + what @pecmsg said

jsda77

Thank you all.

1. motor run but I think it's too weak
2. refrigirent refilled last winter
3. duct work looks not good to me
4. 30years old house, I don't know how old is this central system
5. handler model number is A30-00, no fan control board just relays
6. I will check capacitor first
7. filter, coil is clean - I checked
8. this one for 2nd floor only and controlled by one thermostat(Nest)

Thank you all of you guys.

Any suggestions are welcome!!

pecmsg

jsda77 said:

Thank you all.

1. motor run but I think it's too weak
2. refrigirent refilled last winter
3. duct work looks not good to me
4. 30years old house, I don't know how old is this central system
5. handler model number is A30-00, no fan control board just relays
6. I will check capacitor first
7. filter, coil is clean - I checked
8. this one for 2nd floor only and controlled by one thermostat(Nest)

Thank you all of you guys.

Any suggestions are welcome!!

Do you have the equipment to check it?

jsda77

Dear pecmsg,

Yes, I have fluke 116.

GW

It could be as simple as adjusting the fan speed. How much air you “feel” is subjective, right? Don’t hold your hand immediately below the diffuser, gotta hold it to the right/left a bit. You very well could be low on juice again as well, maybe several issues going on

To set the fan speed gets into more tools and knowing where to stick the drill bit.

jsda77

Dear GW,

I did it (hold, left, right). Almost nothing. I could feel cool temperature but no flowing.

My system doesn't even have a control board but just several relays.

mikeg2015

A bad or very weak run cap will reduce the torque output of the motor and it will run hot. Definitely check it.

Might verify it’s powering the high speed winding, not low speed for fan only.

Can also check amp draw vs. nameplate on motor (if you can read it). 240V motor is around 1.5-2 Amps typically.

GW

Ok you’re saying you have a belt drive? That’s real old school. Is the blower wheel all gooped and dirty? Coil is clean you said?

If you have a belt that’s a pain to change air speed, gotta get different pulleys

You’re sure there aren’t manual dampers that may have inadvertently closed in the duct system?

If it’s direct drive then it should have different “taps”

Paste a pic of the blower motor and or the wiring diagram

And check the cap like we discussed

mikeg2015

Lets take a step back.

What is your temp drop? Is the AC even working properly? PRessures?... or easier ot check, do you have high superheat? What temp is the suction line? Any frost forming on the cap pillars tubes? Whether cold cold, only only part of it? Is charge is low, you’ll have high superheat and part of hte coil will be near ambient temp. Cap tubes can be frost covered sometimes.

How do you know you have too little airflow? ow airflow and you’d have low superheat, resulting in a very cold vapor line and eventually ice forming on the coil.... blocking more airflow and frosting it more.

If it’s belt driven, belt could be slipping

PRR

> I can not feel any air stream from vents. ...told me ...low refrigerant but I don't think so.

You should be able to "feel air flow". Hot/cold air systems are never designed for very low flow because that would require very large ducts and registers.

And certainly "low refrigerant" is not the cause of low airflow. Think of the A/C as a block of ice with a fan to spread the coolth around. Even without the ice you should feel the fan airflow.

As said, some experienced person should stick nose and hands inside the blower unit. There is danger. Electric shock, and getting fingers or neckties caught in spinning parts. It also helps to "know" how fast a motor typically spins and how tight a belt should be. If you are not experienced, it may indeed be wise to "just call the pros".

The other place to look is the ducts. Go in the attic or crawl-hole with the fan running (cooling optional). Your nose-hairs will tell you if there is a leak in the ducting. Remember that many duct installers just buy the right material, go in the attic, and come out when the estimated time is up. Most systems are left with unsealed joints; the home horror sites have pix of totally bogus "duct work". You may be throwing all your cool air in the attic.

The return system is also important. My house had marginal supply ducts but very undersize returns. It was a whole lot happier when it did not gasp for air. Return registers may have neglected filters, or prior children may have been dumping toys down the grill.

A belt-drive system, I think, will not be capacitor-Run but may be capacitor-Start. If the starting cap fails, the motor may erratically "turn" but at a mere fraction of its true speed. I *think* in that case the motor current will be far higher than rated running current (and might burn-up).

Belt tension- there are rules of thumb. If too tight the drive works good but belts and bearings fail quickly. Which leads to too-loose. If 25% of speed is lost in loose slippage, air-flow is down to 50%. Where I worked the HVAC techs ignored the blower-belts in my building and one hot summer I "noticed" that I could stop the slow blower with my hand (do not try this at home!!) When they tensioned the belts it blew good.

The state of the freon system has nothing to do with the fan. Get it blowing before you ask about temperature drop. Running either heat or cooling without proper airflow in the house blower will burn-up the fire or freeze system. (I had an overlarge burner on an undersize duct system- the blower strained but also the fire-box was failing from overheat.)

mattmia2

There is a device called a sirometer that can measure speed from vibration. If the motor was changed a belt drive blower could have cap start, cap run, or split phase.