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Old 12-18-2010, 12:53 PM   #16
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Carrier 58MVP Blower Problem


Sounds more like you have an air flow problem that needs to be corrected. Or your just going to keep burning out controllers.

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Old 12-18-2010, 01:16 PM   #17
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Carrier 58MVP Blower Problem


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Sounds more like you have an air flow problem that needs to be corrected. Or your just going to keep burning out controllers.
Than wouldn't only the resistor burn out?
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Old 12-18-2010, 01:31 PM   #18
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Than wouldn't only the resistor burn out?
More then the resistor can burn out because of low air flow. Just generally the resistor goes before anything else. but not always.

Also depends on how bad the air flow is.
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Old 01-31-2011, 05:51 PM   #19
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Carrier 58MVP Blower Problem


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Originally Posted by bob reynolds View Post
These high efficiency variable speed blower motors are maufactured by GE. They are used in many brands including Lennox, Carrier, Bryant, Payne, York and Trane.

There are two parts to the blower motor.

The two parts are the motor itself and the ECM module that is attached to the blower motor. The ECM looks like a black hubcab and it is attached, to the motor, with two long bolts.

You can remove the ECM module by simply unscrewing the two long bolts. You do not have to remove the blower motor from the mounting.

The motors in different series and brands are often the same. The difference is the ECM module. The ECM module must be matched up exactly or it will not work.

What usually fails on these high efficiency units is the ECM module. A service truck can not possibly carry all of the hundreds of ECM modules that are used in the various brands and series of brands.

However, the part that often fails in the ECM unit is part number SG379 which is a black disc about the size of a quarter in the center of the ECM.

You can look at the SG379 disk and often tell it has failed without any further checking. The disk will often be broken, brittle or disconnected from the circuit board, and there will be an obvious spot on the circuit board that has received a lot of heat. As long as the board is not broken, or deformed and the traces are in place, then this componet can be replaced. This component is designed to take a lot of heat and the circuit board will be discolored from the heat. This is normal and this is common.

This propierity part is a thermistor and it is used for surge protection as well as regulating the current to the motor.

SG379 has a finite life and like a light bulb it gets weaker and weaker until it finally just fails.

Although not available from GE or any or the HVAC companies, a SG379 part substitute, manufactured to OEM standards, is available from amazingkeys.com and can be soldered into the ECM circuit board in about 5 minutes.

If you are a serviceman, you can keep a few of these parts on your service truck and have the unit up and running in one service call and not have to replace the motor or the ECM. This also saves the customer a $1500 blower motor replacement or an ECM replacement.

Bob, thanks. Your info saved me well over $1000 dollars. After a lightening storm and a power outage our Carrier 58MVP furnace would'nt start. I checked for power to the unit and it was good. I set the diagnostics switch and ran the tests. I got the 44 and 41 LED codes no matter what I did. I was about to buy a new control module (around $200) and then a new motor ($800) if necessary. However, I came acrosss the info you provided and opened the control module, looked at the black disk and found it had burned out. A little more research and I learned it was an SG 348 Thermistor. I ordered one from Amazingkeys.com for $20.00 (only place I could find it on the internet). After replacing it everything works fine. You the man!
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Old 02-01-2011, 01:43 AM   #20
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Carrier 58MVP Blower Problem


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Bob, thanks. Your info saved me well over $1000 dollars. After a lightening storm and a power outage our Carrier 58MVP furnace would'nt start. I checked for power to the unit and it was good. I set the diagnostics switch and ran the tests. I got the 44 and 41 LED codes no matter what I did. I was about to buy a new control module (around $200) and then a new motor ($800) if necessary. However, I came acrosss the info you provided and opened the control module, looked at the black disk and found it had burned out. A little more research and I learned it was an SG 348 Thermistor. I ordered one from Amazingkeys.com for $20.00 (only place I could find it on the internet). After replacing it everything works fine. You the man!
Did you bother to check the tolerance on the thermistor? There ar plenty of generic replacements around but they are off spec by as much as 4%.
Know what that will do to the windings?

See you in about a year with a bad thermistor and motor.
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Old 02-01-2011, 07:31 AM   #21
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Carrier 58MVP Blower Problem


Hvaclover, thanks for the heads-up. I'm not savvy enough to check tolerance on a thermistor . Can you guide me or point me to info. Also, what will it do to the windings?

thanks.
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Old 02-01-2011, 03:13 PM   #22
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Carrier 58MVP Blower Problem


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Hvaclover, thanks for the heads-up. I'm not savvy enough to check tolerance on a thermistor . Can you guide me or point me to info. Also, what will it do to the windings?

thanks.
The thermistors are over heat protection for the motor and module.. GE uses very close tolerances on these thermistors. Since China has gotten into the solid state component business we have have been seeing a lot of off spec tolerance
pieces flooding the market from even reputable suppliers.

The thermistors from GE suppliers have a .1 variance. But the knock offs are off by 3-4%. Could make the difference between a motor surviving an over heat condition and burning up.
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Old 02-06-2011, 08:57 AM   #23
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Carrier 58MVP Blower Problem


Excellent Post Bob Reynolds! Very clear. Thank you.

I am not very experienced at soldering - never soldered on a circuit board - but will give this a try. The problem is one of the thin wire legs of the thermasister snapped right at the bottom where it connects into the board. Any suggestion on how to solder the new one on? Alternatively, any suggestion on someone who might be a regular circuit board repair person that I could take this to say a TV repair shop?

btw, the S379 is now $19.99 at amazingkeys.com. Any one find a cheaper source? Would like to get a couple as we have 2 units as this is the second time one of the modules has gone bad. Both units were purchased/installed in 2001. One went out in August 2010, the other in January, 2011. Clearly a design flaw if this one little part is so weak and not easily replaced by plugin Carrier part. Carrier should be embarrassed.
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Old 02-06-2011, 12:42 PM   #24
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Carrier 58MVP Blower Problem


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Originally Posted by redwalsh View Post
Excellent Post Bob Reynolds! Very clear. Thank you.

I am not very experienced at soldering - never soldered on a circuit board - but will give this a try. The problem is one of the thin wire legs of the thermasister snapped right at the bottom where it connects into the board. Any suggestion on how to solder the new one on? Alternatively, any suggestion on someone who might be a regular circuit board repair person that I could take this to say a TV repair shop?

btw, the S379 is now $19.99 at amazingkeys.com. Any one find a cheaper source? Would like to get a couple as we have 2 units as this is the second time one of the modules has gone bad. Both units were purchased/installed in 2001. One went out in August 2010, the other in January, 2011. Clearly a design flaw if this one little part is so weak and not easily replaced by plugin Carrier part. Carrier should be embarrassed.

Carrier should be embarrassed? Why? There are all kinds of reasons your part blew that have nothing to do with the quality of the part.

I have already pointed out that repairing in other posts that Homeowner repair of the motor would void your home insurance if a fire ever occurred. And the blower does not have to be the cause of the fire to void the home owners insurance.

Bob Reynolds makes it sound so easy...

ButI don't see where Bob Reynolds pointed out the chance of extreme injury or death when opening the motor. There are very powerful capacitors he didn't mention that will discharge a dangerous intensity of voltage.

This ECM motor module is not a passive electronic product like a computer or a stereo system.
The ECM module is exposed to the vibrations, surges, over heat of a plugged air filter, ruinously low air flow thru overly restrictive AC coils, over working of the ECM against duct work that is tool small for the ECM to work against.

If you think your hand soldered resistor is going to remain intact against that kind of punishment then go for it.

There is a reason the boards are machine soldered. You get a consistent line of quality and durability much better than hand soldering can deliver.

Just curious, how long have you had this equipment with the defective ECM?
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Old 03-02-2011, 03:00 AM   #25
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Bob, let me add my thanks for your posting. I followed your advice, replaced the thermistor, and now my furnace is working fine again! In my case, I had to dismount the blower motor assembly from the chassis of the furnace to get the ecm off - there wasn't clearance to remove it otherwise - but this was not very difficult. When I looked at the old thermistor, I didn't see any signs of a problem. There was no cracking, discoloration, or anything like that. But since I had already taken it apart and procured the replacement part (I confirm it now costs $19.99) I figured I'd try it anyway, and sure enough it solved the problem.

In answer to some of hvaclover's concerns, I agree that if you have never soldered any components on a circuit board before this may not be the place you want to start. But for the potential saving of $20 vs. $1000 for a repair it may be worth rounding up a friend who has.
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Old 06-25-2011, 01:33 PM   #26
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Carrier 58MVP Blower Problem


Thanks to everyone who posted info on this site and saving me over a grand (another 58mvp with a blown SG379). It is you - not Larry Page from Google or Mark Zuckerberg from Facebook - that make the web valuable.

My contribution to the cause:

1. If you are getting error code 41 (Blower Motor Fault), first follow the diagnostics procedure in the installation manual: verify that the harness to the ECM carries 115Vac (black wires), 12Vdc (red and green wires), and 5Vdc (yellow and green wires). If so, then the problem may very well be the thermistor.

2. The heat that blows the thermistor can also damage the trace on the ECM circuit board (the metal foil underneath the board, to which the thermistor leads are soldered). In my case, the foil was starting to peel off the board. Be careful unsoldering/removing the old thermistor, and instering/soldering the new one. When you insert the new thermistor, make sure you don't tear the foil from the circuit board in the process. Instead of clipping off the excess lead length, I ran each lead in parallel with its corresponding trace, soldering it at component points along the way. This structurally reinforces the trace, and improves heat dissipation.

3. AmazingKeys is great. My blower blew Thursday night, and thanks to this forum I traced it to the thermistor in 30 minutes. Ordered the SG379 from AmazingKeys at 11:30pm, with the message that they notify me if the part was NOT in stock. Joe Friday (anyone on this forum remember the TV show?) from AmazingKeys called me moments later to confirm that they had them in stock, and to offer sending it to me via USPS which has saturday delivery. By noon on Saturday, the family was once again enjoying some nice A/C.
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Old 07-04-2011, 02:40 PM   #27
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I had the dreaded 44 / 41 blower problem on my 58MVP with the motor not spinning after the filter clogged too much..
I took off the ECM and the Thermistor was open, so I ordered one from Amazing Keys and replaced it. The Lands were fine.
Motor now spins, doesn't make any noise except a slight growl when starting up, and still gets 44 / 41. There is also a very slight tick when running. The blower wheel also has about 1/8" variance side-to-side out of center ( Like wiggling back and forth )
I removed the Blower Assembly and inspected the motor. It spins freely and has no noticeable play in the shaft bearings.
When I had it out and separated from the blower wheel, I plugged it in and it ramped up and down several times from low speed to high speed then got the error codes. It was very smooth with no tick noise or other noises.
I'm thinking that something else in the ecm was damaged, but hate to spend the $ for an ECM if it could be the motor.
Also, Is there a way to jumper around the speed detection circuitry to get the A/C back up in the meantime ?

Last edited by ColoradoDave; 07-04-2011 at 04:09 PM.
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Old 07-04-2011, 04:24 PM   #28
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Carrier 58MVP Blower Problem


Ticking noise would most likely be the motor. Could be a magnet coming loose.
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Old 07-04-2011, 04:56 PM   #29
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So, I put the whole thing back together and it came up on fan fine. I then turned it off, put the cover back on and switched it on Cool and it's working now. I'm not sure for how long, though. The ticking noise appears to have gone also. Maybe it was a magnet in the motor and moving it around relocated it back to its' proper place. If it fails again and the ticking returns also, that will be incriminating on the motor, I guess.

One question I have, though, is ;

Is the blower speed error determined by the ECM on the motor and reported back to the main board, or does the ECM on the motor merely report back the speed and the main board determines if that is an error or not ?
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Old 07-04-2011, 05:03 PM   #30
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Carrier 58MVP Blower Problem


As far as I know there is programming built into the motor module and circuit board so they work/talk together. The latest generation of ECM motors all the programming is in the main circuit board and the motors are somewhat generic now.

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