Carrier GE ECM Blower Motor Problem


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Old 08-07-14, 06:57 PM
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Carrier GE ECM Blower Motor Problem

I'm seeking some advice. I was asked to look at an 8 year old Carrier air handler, model FV4BNF003. The blower motor was not working.

The motor is a GE 2.3 ECM type motor. Upon pulling it apart I discovered that a fuseable trace on the board inside of the control module was burnt up. Further investigation showed that two of the MOSFET drivers were cooked.

The motor itself has three leads that plug into the control module. The windings of the motor were right at 2.9 to 3 ohms between each pin on the plug. There were no shorts to ground and nothing smelled/looked burnt so I assumed that the motor was ok.

Ordered a new control module online ($$$). Installed. Verified that the motor spins freely and bearings were ok. Fired up the air handler and put the fan in manual mode. The fan was working fine, running at a slower speed where there was a loud POP and it died. The same fuseable trace in the new control module has now burnt up. Ugh!

I verified the supply voltage to the air handler from the breaker and it looks good. I have a background in electronics and industrial motor controls but am unfamiliar with HVAC controls.

Any ideas why the second control module blew?
 
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Old 08-07-14, 10:50 PM
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Welcome to the forums.

Those motors are great when they're working normally but when they fail

Did you check the motor windings between each other and ground again ?
Is the blower spinning freely too ?
 
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Old 08-08-14, 05:24 AM
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The blower spins freely, no resistance at all. I did check resistance from the windings to ground using a DMM. I measured infinite resistance.
 
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Old 08-08-14, 05:40 AM
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I have read a variety of winding resistance values online for this motor. Mine is a 1/2HP model.

What should I expect to measure between and of the 3 pins on the motor portion? I suspect that the motor itself may be bad.

Edit: After posting this I found the following ECM manual online. According to it, my resistance measurements are below 20 ohms and within 10% of each other so they are ok.
 

Last edited by Jeremy S; 08-08-14 at 06:19 AM.
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Old 08-11-14, 06:02 AM
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I am going to try to get the control module replaced but before installing another I'd like to verify that it was a factory defect that caused the other to fail versus a problem in the furnace itself.

I'm still looking for ideas of things to check. I measured the 24v voltage at the control board and it seemed to be correct.
 
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Old 08-11-14, 06:22 AM
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If the external static pressure it over 1" water column you will continue to go through motors until you correct the ductwork problem.

If you have a Carrier Infinity system the static pressure can be displayed at the Infinty thermostat.
With a standard thermostat model you need a manometer to measure the external static pressure.
You must have a working motor to check the external static pressure.
 
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Old 08-11-14, 06:53 AM
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This has been a working system since 2006 until this motor falied. I have no way of measuring static pressure. What could have changed that would effect static pressure?

Can a fan control module fail in a way that it will cause blower motors to fail? For example, trying to force the motor to operate at two speeds at once.
 
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Old 08-11-14, 07:11 AM
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Much more likely to be high static pressure. Those expensive 1 inch pleated filters can be very restrictive. A basic pleated filter is much easier on the motor. Dirty coils can also cause a problem.
 
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Old 08-11-14, 09:09 AM
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Look inside the motor and make sure the magnets are still intact on the rotor.
 
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Old 08-11-14, 02:32 PM
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Magnets are still intact and motor spins freely.
 
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Old 08-12-14, 05:10 AM
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When I work on it again I will clean the coils out if they need it and check the filter.

I am gun shy of installing another $300+ control module on this motor and having it cook just a few minutes after starting it up. That is why I want to verify that everything else electrically is fine.

Supply voltage tested good at 240V with a good ground.

Motor winders measure good. Motor magnets are intact and motor spins ok.

At the fan control board I ran through the various modes and measured 24V on the correct terminals each time. I'm not sure what to measure on the other pins of the 16 pin connector.

I am going to verify voltage again at the load side of the breaker and at the 5 pin connector at the motor.

If I get a new control module I would like to find somebody locally who could test the motor and controller for me using the correct test tool.
 
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Old 08-20-14, 06:31 PM
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So I finally got this resolved.

I had a HVAC Technician take a look at it. He verified that the ECM 2.3 module that I had purchased was bad, but could find nothing else wrong in the system.

Last weekend I was at an auction of a former HVAC/Plumbing business where I found a matching 1/2HP GE 2.3 ECM motor, but with a different part number. Just for fun I tried that motor and controller and it works fine in the furnace! I'm not sure what it is programmed for, but is has been working fine all afternoon and moving a decent amount of air.

As for the supplier where I purchased the module that instantly stopped working.. Caveat emptor! The technician seemed to think the replacement controller was defective from the factory, yet the supplier refused an exchange or RMA. After sending them a copy of the invoice from the technician with his diagnoses of the system, they agreed to an RMA but with a 50% restocking fee.

Perhaps my experience with this repair if I had chosen a better supplier to begin with...

NorthAmericaHvac.com - Best Price on all HVAC Parts!

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