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Billy, HVAC Technician
Category: HVAC
Satisfied Customers: 20946
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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First Ill start off by giving you all of the model and part

Resolved Question:

First I'll start off by giving you all of the model and part numbers that I could find on my unit. I have a Carrier Weathermaker 8000 Variable Speed 58UHV030-16 serial # XXXXX the control board is HK42FZ010, the Airflow Selector is CESO130028-00, the outdoor unit is a Carrier 38TXA048300.
The problem is a couple days ago the blower stopped working. I had a local Carrier repair tech come look at it and he replaced the ECM on the blower motor (the thermistor had burned off). Now the blower runs, but there is almost no airflow. Now when I say that "there is almost no airflow" I mean at either the return or the ceiling vents. (The return vent is one large vent directly below the platform that the unit sets on; all of the air vents are in the ceiling.) The problem persists even if I take the air filter out of the equation (out of the unit). I have also taken the cover off of the box on top that houses the air conditioner coils and they look clean and are free of ice. (The tech that came out seemed to think the lack of airflow was a blockage here; I disagree, if the blockage was here, that would explain the lack of airflow at the ceiling vents, but not at the return.) If I turn it on the larger pipe on the outside unit will get covered in ice; the tech thought that maybe I was low on refrigerant, but that checked out OK. Also, we tried the heat and that starts its cycle then kicks off due to a thermal protect (code 33). Although I didn't check at the time, I think the coils inside were probably freezing up (when the pipe outside was freezing). My thoughts are both the problem with the AC and the heat are attributed to a lack of airflow and my conclusion is that the blower is not spinning fast enough.
For me, this narrows it down to : a bad Control Board, a bad Airflow Selector, or a bad blower motor. Personally I think it's one of the two circuit boards, although I've examined both and don't see any burn marks on them.
I am pretty handy with electronics; I have a multimeter that I could do some tests with if I knew what (or where) to test. Also, I probably could have replaced the thermistor (I can do soldering) and saved about $400.
I guess the answer that I'm looking for is "where does the problem really lie?"
I don't want to waste a lot of money randomly switching out parts or doing unnecessary work (I'm sure my bill with the Tech is already over $500).
If the problem is with any of the above mentioned parts, I can replace any of those myself.
Any help you can provide would be great.
Submitted: 2 years ago.
Category: HVAC
Expert:  Billy replied 2 years ago.

On the motor is a 16 wire plug and then a smaller plug.

If you unplug the 16 wire plug what does the motor do when powered on?


Customer: replied 2 years ago.

OK, I unplugged the 16 wire and left the smaller one plugged in; Thermidistat set to "cool" with fan "on" and the blower does nothing. (I thought I heard a relay on the board click, though.)

Expert:  Billy replied 2 years ago.
Thank you,

please give me the number off the ecm module.


Expert:  Billy replied 2 years ago.
And before I forget

ECM Testing Manual


Customer: replied 2 years ago.

There is a sticker that says GE 04/18/98 BF06 3TCV.

Expert:  Billy replied 2 years ago.
thank you,

call the tech back as it appears the module is the incorrect one. The modules must be exact to the make and model furnace, circuit board and motor. The module you have has a diffent program in it.

Have the contractor verify and show you that new module is indeed a match as far as programming

Billy, HVAC Technician
Category: HVAC
Satisfied Customers: 20946
Experience: Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
Billy and other HVAC Specialists are ready to help you
Expert:  Billy replied 2 years ago.
The correct module will be a RMOD44AE120

Shown here 58UHV module

The one you have is listed as 230v fan coil unit shown here.

Please see list of furnace units (115volt) shown as using the module HERE

Customer: replied 2 years ago.

Thanks for all your help. Tim (airheatman) seemed to think that the module was correct, however I did a search (after looking at the links you provided) and I agree with you that the module is probably not the correct one.

I did numerous searches and I can't find the "BF06 3TCV" module; all I can find is "BF06 2ZVU" and "BF06 39VM" which are both 230v modules so this would lead me to believe that (even though I couldn't find it) the module the Tech installed is probably for a 230v motor as well. The 5 pin plug on my motor has the jumper from 1 to 2, which according to the ECM manual that you sent me means that my motor is 120v (page 11/12).

Again thanks for all your help, I hope I can get this all resolved tomorrow.

Expert:  Billy replied 2 years ago.
Please let me know if you need any follow up at all.

I apologize for delays today.


Customer: replied 2 years ago.

No problem with any delays; I've been busy doing other things as well.

Just wish I would have known about the part numbers a little sooner; I had the blower out and the module off. No big deal, they come out easy enough.

Thanks again.



Monday I called the Tech and asked for my old ECM back. He asked if there was a problem and I said "yes, you installed the wrong ECM on my motor and it doesn't work properly." He wasn't real happy and told me that he had pulled that one off of a motor at the shop and thought it would work. I explained that these are programed specifically for certain models and this one was obviously wrong. I told him that I intended to fix it myself and his services were no longer needed.

I ordered a new thermistor (the part that burn off) from Mouser Electronics (EPCOS Inrush Current Limiter part # XXXXX; about $5.50 for the part and about $8.00 for shipping). I got the part today, got it soldered in and everything put back together. It was about 90 in here when I got the AC running and about a half hour later it's down to 85; slowly but surely cooling off. At least the blower is moving plenty of air now.

Thanks again for all your help. And for anyone else who has the ECM on their variable speed blower "go bad" : check for a burned off thermistor. If your (or someone you know) soldering skills are OK, then I'd recommend doing this (for about $15.00) before you replace the entire ECM (for about $400.00 plus a service call and/or repair charges). It's not hard to do, and so far, so good.

Thanks again.

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