Air Handler Blower speeds up then slows down

Problems related to residential installations.

Air Handler Blower speeds up then slows down

Postby JohnRoss » Fri Sep 21, 2012 8:53 am

Tempstar Air Handler FXM4X4800A1 Installed 09/2010.
Tempstar Heat Pump TXH548GKA100 Installed 09/2010
A/C system controlled by Carrier Comfort Zone 4 Zone System installed in 1992.

When AC comes on the Air Handler Blower runs for about 20 seconds then stops for 3 seconds then runs for about 20 seconds. This happens the entire time the system is running.

I turned the thermostats Heat Switch Off & the Cool Switch Off and turned the fan Switch from AUTO to ON & the blower motor did the same thing, blower runs for about 20 seconds then stops for 3 seconds then runs for about 20 seconds.

NO burning or other smells coming from the AC unit.

I opened the air handler service panel and this unit has a ECM Motor.

The blower wheel (squirrel cage) spins freely and is quiet.

The evaporators metal housing has what appears to be rust on the side under each of the copper lines where it comes out of the evaporator and goes back in. Not sure if this is normal for a 24 month old unit?

The evaporator coils fins are clean.

Other than shutting off & turning back on problem the system runs fine & the house is cool.

All three filters have been replaced.
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- Air Handler Blower speeds up then slows down

Postby Freon » Fri Sep 21, 2012 4:52 pm

What is the date this behavior started?

Before it started, did you have any work done on the air handler, condenser, ducting or your house?
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- Air Handler Blower speeds up then slows down

Postby JohnRoss » Fri Sep 21, 2012 5:51 pm

It started when I went in my attic, this part of the attic is not close to the air handler & no work done on the air handler, condenser or ducting in my house.
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- Air Handler Blower speeds up then slows down

Postby Freon » Sun Sep 23, 2012 2:02 pm

If you go to the air handler and open the blower compartment and smell the open end of the motor, does it smell like burning rubber? It's possible the windings are slowly shorting but you'd need to take the motor to a shop to know for sure.

With power off, spin the blower wheel (squirrel cage). Does is spin freely and quietly? You might run the blower with the door open to look and listen while it runs. There should be a switch at the door opening you'll have to press manually. Possibly the motor bearings slowly bind as it runs. You should be able to hear that problem.

Another possibility is the run capacitor is failing (assuming a PSC motor). It's not expensive and easy to replace. I'd start there given the age of the system. Be sure to buy an IDENTICAL capacitor... take the old one with you.
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- Air Handler Blower speeds up then slows down

Postby JohnRoss » Sat Sep 29, 2012 3:04 pm

NO burning or other smells coming from the Air Handler & rhe blower motor spins freely and is quiet & DOES NOT have a run capacitor.

I noticed the evaporators metal housing has what appears to be rust on the side under each of the copper lines where it comes out of the evaporator and goes back in. Not sure if this is normal for a 24 month old unit?

The evaporator coils fins are clean.
JohnRoss
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- Air Handler Blower speeds up then slows down

Postby Freon » Sun Sep 30, 2012 1:17 pm

If there's no run capacitor you mush have an ECM motor. Google ECM motor to learn more about it. The idea is the rpm will adjust to the load. Sadly I am not knowledgeable in those types of motors.

The rust in the evaporator coil is common. There will always be rough edges where metal is cut during manufacture and the water from the condensation will cause it to rust. As long as the fins are clean, you're good to go. You've been changing your filters and that's why the fins are clean.
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- Air Handler Blower speeds up then slows down

Postby JohnRoss » Mon Apr 29, 2013 12:59 pm

JohnRoss -
> Tempstar Air Handler FXM4X4800A1 Installed *.
> Tempstar Heat Pump TXH548GKA100 Installed *
> * system controlled by Carrier Comfort Zone 4 Zone System installed in
> 1992.
>
> When AC comes on the Air Handler Blower runs for about 20 seconds then
> stops for 3 seconds then runs for about 20 seconds. This happens the entire
> time the system is running.
>
> I turned the thermostats Heat Switch Off & the Cool Switch Off and
> turned the fan Switch from AUTO to ON & the blower motor did the same
> thing, blower runs for about 20 seconds then stops for 3 seconds then runs
> for about 20 seconds.
>
> NO burning or other smells coming from the AC unit.
>
> I opened the air handler service panel and this unit has a ECM Motor.
>
> The blower wheel (squirrel cage) spins freely and is quiet.
>
> The evaporators metal housing has what appears to be rust on the side under
> each of the copper lines where it comes out of the evaporator and goes back
> in. Not sure if this is normal for a 24 month old *
>
> The evaporator coils fins are clean.
>
> Other than shutting off & turning back on problem the system runs fine
> & the house is cool.
>
> All three filters have been replaced.


I just found a VERY Honest HVAC repair company that quickly diagnosed this problem today 04/29/13.

A component inside the X-13 blower assembly motor was bad. The technician told me Tempstar has had a lot of problems with the X-13 motor and he has replaced a lot of them.

AC is now up and running without shutting off every 20 seconds as it did before.
JohnRoss
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- Air Handler Blower speeds up then slows down

Postby juster » Mon Apr 29, 2013 2:52 pm

Great thanks for the update
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