ECM 2.3 Variable Speed Blower Motor Troubleshooting

By | September 7, 2016

ECM 2.3 Variable Speed Blower Motor Repair Replacement

ECM 2.3 Motors are used in HVAC systems frequently these days as blower motors.
This includes air conditioners, heat pumps, and furnaces. It can adjust the air flow depending on what the system is getting for feedback.
First of all there are two components to a ECM motor the control module and the motor itself.
ECM 2.3 Variable Speed Blower Motor Replacement
The motors by far fail the most but the control modules can also fail.
If the motor fails than it can simply be replaced. If the control module fails it needs the chip to be programed for the unit.
ECM modules have a common failure which is a thermistor which goes bad and is a common for these to fail.
ECM 2.3 Variable Speed Blower Motor Repair
Basics Steps to Locate the Problem with a ECM Motor
Caution must be taken when dealing with any HVAC system as there is high voltage in any system. Do not attempt to repair a unit yourself unless you have had training in proper high voltage pratices and safety.

1…Set the thermostat to Blower which should send 24 volts to G (blower) and C (Common). Be sure 24 volts is being supplied at the G (Blower) and C (Common) terminals.
2…Be sure there is high voltage 120 volts or 220 volts. Use a multi meter and verify the motor is getting power.
3…Power the unit off at the breaker. Separate the control module from the motor. Three wires which go into the motor should be tested for resistance one to the other.
ECM 2.3 Variable Speed Blower 111
This is checking the motor windings are good and each resistance value should be close to the other with-in 10 percent.
Also check each leg of the motor wires to the case to see if one has shorted out.
4…If the values are wrong than the motor is bad. If the values are correct and the motor spins good than the ECM is likley bad.
The above are simple steps to help narrow a down a problem on suspected bad ECM motor.
There are more test that can be done including with the right diagram for your motor jumping the harness to get the motor to run.
More than likley it will be a bad motor as this is the most common failure and it will need replaced.
ECM control modules do fail though so be sure to verify it has gone bad. Remember the control module is programed to work with that unit so it must go back on a new motor.
There is a common failure on ECM motors with the thermister going bad. Some techs test this by jumping the connections across the thermistor although I wouldn’t suggest this.
Control modules should be bought from the manufacture. Remember a 2.3 module from Rheem cannot be used on a 2.3 motor for a Trane system even if they look the same.
There are many problems that a ECM motor can have. Sometimes it is simply a pin on a molex connector the needs pushed in, other times the entire unit can be bad.



7 thoughts on “ECM 2.3 Variable Speed Blower Motor Troubleshooting

  1. Ryan

    I just picked up a new ecm motor for a lennox. I wanted to test it before putting it in so I used my tecmate inspect. To test it.
    Connected the 16point harness and the 24 volt leads to the 24v side of the transformer. Turned on tecmate. Motor start but it ramps up and down about 5 times and then quits spinning. Voltages and ground are.all good. Also tried jumperimg the motor though the 3 and 15 pins on the harness and wiring the 120 direct to another power source bypassing the furnace all together. Same result. Could the new module and blower be faulty. Module portion, tjermosto or capacitor?

  2. SAm

    Very helpful! I used this to find a blown Thermistor on my GE ECM control module. The part is labeled SG348, but I cannot find that exact part number to purchase. Do you know what would be the correct replacement thermistor part number or spec? Thanks–I hope this fix works!

  3. Martin Balent

    I have a Rheem RH1T3621MTANJA, the fan doesn’t get up to speed. It starts very slow and stops about 5 seconds later. I replaced the ECU board and had the motor reprogrammed, which it said it accepted it. Do you think the ECM is bad?

  4. ERIC

    If replacing ecm module does the supplier need to program it to my unit?

  5. Jeff Black

    @Rick H
    You have a sticky resistor. Can hit it to work but will need to be replaced eventually.

  6. Rick H

    I have a Rheem home ac and the air handler fan motor will not shut off. The thermostate has been tested and it is fine The only way to shut off the fan is to shut off the breaker . I suspect it is the ECM module. Can this alone be replaced or does the entire unit need to be replaced? Where to buy? Thanks.

    1. Kevin Young

      I have the same problem. Older Rheem Classic 4-ton RHLA-H4821JA. Will not turn off, even with thermostat and control board disconnected. Starts and stops randomly. Heat and A/C operate correctly. Are there any other potential trouble spots to look at before purchasing a new ECM module?


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