In need of some help/advice please! I have a 3200 sq ft house with 2 identical units. Both are original to the house built in 2007.
Carrier model: fx4cnf030000aaaa

This is the FOURTH time in 6 months something has gone wrong with the downstairs AC.

1st time: the part in the air handler that goes from the unit to the ceiling/attic was not installed correctly, so the AC guy fixed it.
2nd time: Outdoor unit capacitor replaced.
3rd time: Coils covered in dust even though they were cleaned just two months before by AC tech.

Now, I'm out of patience and money, so hopefully someone can help so I can do this myself.

The blower motor in the air handler is just barely turning, no air coming through the vents. There is not a capacitor on the motor. Is there always suppose to be one? Coils are clean, thermostat is getting correct voltage, filters are clean/new and changed once a month.

Any ideas what could be wrong? I really appreciate any help! In San Antonio, TX, and the heat is not nearly over!

 

Welcome to the forums!! I believe you have an X13 blower motor in your air handler. On that type of motor it is usually the module on the end of the motor that goes bad. Usually (but not always) it is a thermistor inside the module that fails. It is actually a relatively easy repair. Here are two links to threads that discuss the issue. The second thread has links to a video on how to repair it if the thermistor is the problem as well as a source for the thermistor.
http://www.doityourself.com/forum/ai...ble-motor.html

http://www.doityourself.com/forum/ai...wont-turn.html

Here are links to info that may be helpful also:

http://dms.hvacpartners.com/docs/100.../FX4C-07PD.pdf
ftp://ftp.mingledorffs.com/Tech_Serv...BlowerDemo.pdf

Can you post the model number of your blower motor? Photos would also help to identify the motor.

 

Hi,
Thank you for your response.
Model number to the blower is FX4CNFO30.
And just out of curiosity, can you tell me if it's normal not to have a capacitor on it?

 

These motors do not have an external capacitor. I meant for you to post the model number off of the blower motor itself.

 

Oh I'm sorry, I thought that was it. I will do so tonight when my husband gets home and takes it out.

 

The model number will be shown on a label affixed to the motor as outlined in attached photo. Some versions of the motor are reparable by replacing the thermistor and others are not. I believe it is version 2.3 that is reparable.

If your husband has a voltmeter he can do the basic voltage tests that are outlined in the link in my previous post:

ftp://ftp.mingledorffs.com/Tech_Serv...BlowerDemo.pdf

Also, make sure the shaft of the motor turns freely.

 

I was able to remove the unit, but I don't know how to get the motor out. I'll get the actual model # asap.

 

The photo is not clear enough to read the model number. Also, make sure the air filter in the unit is clean, all vents are open and the air return vents are not blocked as these motors will not work well with any type of air restrictions.

 

I believe the attached photo of a module is similar to the one that fits your blower motor. The thermistor, that sometimes is the cause of the issue, is the part circled in white. This module is the type that has the printed circuit board encased. I am not sure if that can be removed to work on it.

 

Here is a photo of the blower motor Model #.

 

Thanks for the photo. I see some rusted areas on the motor. Several years ago these motors were having a lot of failures due to moisture problems.

When testing the voltage at the harness plug make sure there is a call for cooling at the thermostat.

 

I recently purchased a house with a Carrier FX4C blower installed in 2007 and the same exact problem (when calling for either heat or AC, the fan relay switches on and the blower motor just barely turns - it actually sputters, going a little very slowly and then stopping). I can't smell any burning and the unit is totally clean inside (i.e., no dust on fan blades). The fan blades spin freely.

Following this thread very closely.

 

X13 Troubleshooting - YouTube

 

Welcome to the forums:

The OP never posted back with an update. Have you done the diagnostics as outlined in the video you linked and reviewed the info in post #2 and #6 in this thread?

 

Thanks for your reply!

I took a look at the video and used the tips to diagnose that it, in fact, is the blower motor that is not functioning (i.e., high and low voltage leads to motor are within spec.)

So, while I think the problem with my X13 was a blown capacitor, I was unable to diagnose because the PCB in the end bell is factory sealed with a thick coat of black rubbery goo. I ended up ordering a new motor assembly from ebay for $330. Sucks but still beats the $1100 I would have paid for a HVAC repair visit.