You are here:

Heating, Air Conditioning, Fridge, HVAC/Air handler fan doesn't blow constant


QUESTION: My air handler fan spins erratically. It doesn't spin constantly.Fast and slow.
  I shorted the R and G terminals at the Thermostat and it still reacts the same. I changed the control relay and transformer...same result. The voltage at the control relay when A/c is on is 24 for one wire and 15 volts on the other coming from the transformer.
The fan spins freely when pushed by hand and the voltage  to the fan is 257 volts which I know is high but it wouldn't make the fan react like this I don't think. Outside unit runs.
 I took out the motor and tested it for short against the body (none) and the ohms were all the same for all three connectors so the motor 's fine.
So I'm guessing the control on top of the motor is bad. What am I missing? Motors cost $3-4 hundred dollars Tell me there's something else it could be PLEASE!!!

ANSWER: Enrique,

Bypass any relays, and board and wire the two motor leads  direct to the power that feeds the air handler ( basically the shut off switch at the AH turns it on and off Reference the wiring diagram ) to your not normal high voltage and see how the motor runs. Verify the run capacitor is not leaking or bulging. Odd how you can have such a high voltage if this is a residential home. As far as the cost of a motor that price maaaay be for OEM motor, but a nationwide Company sells motors to the public, ( needing a account set up )for less than half that price including capacitor. Usually motors run at 10% difference of rated voltage, yours exceeds the 10%.

---------- FOLLOW-UP ----------

QUESTION: I haven't seen a run capacitor anywhere in the air handler. I have an x3 motor.One of those motors with a control module on the motor. Maybe those  types of motors have the cap built in the control module. I don't know but no run cap.
 I don't know what AH stands for so I don't know where to turn on the motor.I know that the Ecm has 2 plugs on it. One with 2 120v wires, a ground wire and a blue 24 volt wire from the transformer. The other(speed taps) has 5 wires of which only one wire (purple 24 volts from control relay)is powered. How do I wire it?


You did not mention you had a ECM motor initially so i thought you had a standard multi speed motor, yours sounds like a variable speed motor Variable speeds do ramp up and down in rpm whereas a multi speed runs one constant speed.ECM motors are certainly more expensive than the standard motors and more complicated.AH stands for air handler. Your fan may be working OK once the room close to the t-stat set point the blower fan ramps down.Try finding info on your AH and read how to set the motor up. Also a troulbeshooting guide.for your brand model AH. For me to tell you if your system is working OK via internet is difficult. Those type of system are difficult to troubleshoot via internet.

Heating, Air Conditioning, Fridge, HVAC

All Answers

Answers by Expert:

Ask Experts




40+ years diversified experience.An HVAC/Refrigeration Self Employed Contractor since 1986. NATE Certifield. Answer questions pertaining to Residential and Commercial Air Conditioning , Warm Air Heating, Heat Pump systems.Mechanical and Electrical troubleshooting of these systems.Be as detailed as possible when describing problem.Packaged unit or split systems.No appliance questions.


Installation and Troubleshooting, Mechanical and Electrical, in following areas, Refrigeration ( Walk In and Reach In Coolers and Freezers ) Commercial Roof Top and Packaged Heating/Cooling ( Natural Gas,Propane, Electric, and Heat Pumps ) Computer Room Air Conditoning Systems,Commercial Residential Packaged and Split Systems Air Conditoning and Heat Pumps.Warm Air Oil , Natural and Propane Gas Heating systems.

Graduated from Private Technical School in 1975. An HVAC/Refrigeration Contractor . Have Unlimited Heating/Piping and Cooling Contractor License.Limited Sheetmetal Contractors License.NATE Certifield. York Certifield Master Heat Pump Technician 1986. Served 33 years combination Active Duty Air Force , Air Force Reserves and Air National Guard in the HVAC/Refrigeration Shop/Mechanical Shop. Troubleshooting/Installing HVAC/Refrigeration Equiptment Worldwide. Retiring in 2003 as a Senior NCO ,and a Mechanical Superintendent.

©2017 All rights reserved.