Variable speed blower speeds up and down.

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Old 11-05-11, 03:47 PM
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Question Variable speed blower speeds up and down.

My blower fan is surging and does not reach full speed, it oscillates between fast and slow trying to reach full speed. Last year it was working normal and i would just hear the speed increase until it reached full speed. Unit is Nordyne G7TC 95% with variable speed blower. I suspect blower control board or motor itself. How can I prove one or the other?
 
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Old 11-05-11, 04:27 PM
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Question GE ECM Motor speed surges

Has anyone heard of these blower motor surging while trying to reach full speed. Blower speed constanly trying to go faster then drops down slow again every few seconds. Do I need to replace blower motor, cap on the motor or the control board?
 
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Old 11-05-11, 09:53 PM
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Gary, I believe these two threads which I merged are referring to the same problem?

Is this a HOT AIR furnace?

If so, I will move it to the proper forum... this is HOT WATER and STEAM here... let me know
 
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Old 11-06-11, 07:17 PM
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Originally Posted by NJ Trooper View Post
Gary, I believe these two threads which I merged are referring to the same problem?

Is this a HOT AIR furnace?

If so, I will move it to the proper forum... this is HOT WATER and STEAM here... let me know
Yes this is a gas furnace, Sorry new to the forum.
 
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Old 11-06-11, 08:46 PM
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Might be a dumb question...
Have you checked your filter ?
ECM fans will ramp up to overcome filter restrictions, yours might be clogged and / or torn.

diagnosing the control board is not likely a DIY item.
 
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Old 11-07-11, 03:47 PM
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I just looked over your furnace manual and do tend to agree with TO that it may not be a DIY job... if (and it sounds like good advice from TO) the problem is not the filter clogged.

It could also be a problem with the wiring from the blower to the controller, or even a problem with the blower itself. I believe that there are speed sensors (based on what I looked at in the manual) on the blower that send feedback to the controller. Perhaps that sensor is on the fritz... or it could even be something as simple as a dirty connection...

Another thought... some motors have oiling points that want a few drops of oil every year... does yours?

In any case, I'm afraid that you are gonna get 'fleeced' if you call a repair guy.

Unless the gent is well versed in your particular furnace, he will most likely just start 'throwing parts at it' without diagnosing.

Puts you in a tough spot... what happens if the tech says you need a new control board for multi-megabucks... and it DOESN'T fix the problem? Maybe you want to make it perfectly clear right up front that you aren't going to pay for any parts that don't fix the problem. But then, you risk pi55ing or scaring the guy off and then yer stuck...

It might be worth a call to Nordyne, or a look on their website to see if you can find a 'troubleshooting tree' that includes symptoms and possible solutions.

But check the filter first...

Moving you to the furnace forum, hopefully someone there will know your unit.
 
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Old 11-11-11, 03:42 PM
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Problem has been solved.
Short story: it was the blower control board.
Long story: I pulled the blower out of the furnace and found water line inside the furnace from huricane Irene. I lost electricty for about 36 hours and had about 8 inches of water in basement. The blower motor was completely above the water. The blower control board mounts horizontally and the bottom 2 inches were under water.
Once the blower control board was out, I found 3 10k resistors with legs burned completely off. Ran to Radio Shack and picked up pack of 5 for $2.49, soldered them in and threw it back together. Blower fan speed is back to normal, steadily climbs to full speed.
If I have any more trouble with blower speed I will replace the board, but it is working right now.

P.S. Furnace is only 3 yrs old and still under warranty, but nobody covers water damage.
 
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