Carrier ECM Blower Motor Issue

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Old 08-12-15, 08:40 PM
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Carrier ECM Blower Motor Issue

So I have a problem with the blower motor on my furnace. I checked it out, and the fan will rotate a little forward, stop, then rotate backwards a little.

I was digging through the forum and found some good information, http://www.doityourself.com/forum/ai...e-motor-2.html

It has a SG349 Thermistor (a 1ohm), which I've heard can be a common issue. I checked it and at room temperature it is 1.6-1.8ohm. Does anyone know what the range one of these should read?

Some info:

Furnace: 58mvp100-20

Motor: HD52AE120

Any help would be great, I'm trying to avoid a $1000 motor assembly purchase.

Thanks,
Mitch
 
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Old 08-12-15, 10:40 PM
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Welcome to the forums.

That part is rated for 1 ohm +/-20%. So that would be .8 ohm - 1.2 ohms.
It looks like it may be starting to go bad.

Here's some specs on an identical part....
SL32 1R030 Ametherm | 570-1059-ND | DigiKey
 
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Old 08-13-15, 04:03 AM
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Thanks. I guess I also forgot to mention that I didn't remove the thermistor before measuring across it. The power source was disconnected though. Is it possible to temporarily jump across the thermistor to make sure that's the issue before I wait for parts?
 
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Old 08-13-15, 04:19 AM
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Yes, you can temporarily jumper across the thermistor to try it. The thermistor is an NTC (Negative Temperature Coefficient) type, meaning that it's resistance goes down as its temperature goes up. It is used as a surge limiter, limiting the inrush surge current when the motor is turned on. Be aware that shorting the thermistor puts more stress on the other components (nothing to limit the surge current), so there is a chance of damaging the other components. However, I have heard of people who have jumpered the thermistor while waiting for a replacement part to come in.
 
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Old 08-13-15, 03:36 PM
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The trick to jump it didn't work. Should the motors freewheel easily, or should there be some resistance to it? Is there a way to check the motor, there are only 3 wires going to the motor itself?

The local heating and cooling place can get me the controller module for about $300, but none of the electronics look visibly burned out.
 
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Old 08-13-15, 03:59 PM
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I'm not sure what you're asking regarding freewheeling. The motor shaft should turn easily when not powered up. Of course, when it is powered up, it should be turning. However, with an ECM motor, there are electronics that drive the motor. It's not like a simple AC motor where you just apply power to it.

When the ECM motor died on my furnace last January, the tech that came out to repair it (it was under warranty) said that there was an "ECM motor tester". He said that he didn't have one, however the other techs at this HVAC company did have them. So, there is a way to test the motor/control module.

The tech told me that the failed motors he had seen all had burned out thermistors. Sure enough, that's what was wrong with my motor. In your case, it's not the thermistor, particularly since you see some movement (it's getting power). In all likelihood, your problem is either with the control module on the back of the motor, or the furnace control board (electronics that send the timing signals to the motor control module). I don't know if you could bring your motor & module to a HVAC dealer and ask them to test the motor/module. It would cost you something, but it's probably better than paying $$$ for something that may not be the actual problem.
 
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Old 08-13-15, 05:04 PM
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Basically, I just meant that I can rotate the motor but it doesn't "free wheel". I'm guessing the magnets in it prevent that.

So if there is rotation at all, the thermistor must be OK?
 
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Old 08-13-15, 06:23 PM
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http://dms.hvacpartners.com/docs/100...58MVP-15SI.pdf

Rotating the shaft only indicates that the bearings are okay.
You can also remove the two 1/4" hex head screws that connect the module to the motor to separate the motor from the module.

Unplug the module from the motor and measure the resistance between the 3 motor wires. L1-L2, L1-L3, and L2-L3. They should have the same resistance.
You also want to measure each leg to the body of the motor. The manual reads something like greater than 75K ohms but I would expect infinity.

I use my Tecmate ECM tester before those tests.

The older ECM 2.3 and 2.8 motors with a 16 pin connector allowed you to measure between 1 and 6 for 10 volts DC with a Y1 demand present but the new ECM does not have a 16 pin connector. ( so no analog test available)
 
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Old 08-13-15, 06:39 PM
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I must have read your mind, because I was just in the middle of checking that. L1-L2: 4.3ohms L2-L3: 4.7ohms and L1-L3: 2.0ohms. All show OL to the body. So that points to a short circuited coil, correct?
 
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Old 08-13-15, 06:45 PM
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It rules out the motor. That leaves the module or the control board as the culprit.

Is SW1 switch 1, 2 and 3 in the off position?

What codes do you get if you turn on SW1 - 1?
(Probably a little late for that now but I suspect 44)

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Old 08-13-15, 06:56 PM
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But if L1-L3 is 2.0ohms, isn't that a problem since its less than half the resistance of the other two?

I'm not sure how to read the codes. I'll flip through the manual you sent and see if that tells me.

Thanks, for your help btw.
 
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Old 08-13-15, 07:10 PM
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Yes, 2 ohms is a bad reading if the other readings are running closer to 4.7.

Old eyes.

SW1 is the largest set of toggles. I highlighted them red.
If you turn on SW1 switch number 1 it brings up past trouble codes.

 
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Old 08-13-15, 07:21 PM
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Bad enough that its probably the smoking gun?
 
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Old 08-13-15, 07:31 PM
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Yep, a 50% difference is too great.
I would double check those reading though.
It seems like I read around 2.7Ohms on the last 3.0 ECM motor that I tested.

Could be wrong. It has been a very hot summer and my head feels the effect of hot roofs and attics.

I wonder if that motor is still on the warranty shelf at my shop.
 
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Old 08-13-15, 07:52 PM
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Yep, as confirmed by two (admittedly cheap) multimeters. Near as I can tell, replacement seems to be pretty much the only solution for the motors.
 
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Old 08-13-15, 09:16 PM
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10% is the acceptable range when checking phase to phase...

 
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Old 08-15-15, 09:02 PM
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I have a carrier central air unit. The blower motor is GE ECM X13 1/2 HP 230 VAC. The motor rotates very slow or sometimes barely rotates at all. What could be the problem ? The local HVAC guy mentioned that he would need to replace my motor . I would like to give myself a try.
Can someone please guide me in right direction ?
 

Last edited by Joel Dmello; 08-15-15 at 09:18 PM.
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Old 08-15-15, 10:47 PM
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The ECM X13 is sold as a one piece assembly.

Verify line voltage to the high voltage terminals and 24 volts to the low voltage terminal.

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Last edited by Houston204; 08-15-15 at 11:02 PM.
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Old 08-17-15, 12:03 PM
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Thanks for the response and the information. The voltage seems okay. Does that mean that the motor needs to be replaced. Is there any thing inside the motor that I can troubleshoot or validate ?
Since its rotating very slow, I am hesitant to conclude that the motor is bad.
PLease advise.
 
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Old 08-18-15, 07:59 PM
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The manual states that replacement is required at this point.
I would replace the motor.
 
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