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dhigginx 06-15-2011 02:14 PM

Blower won't start
Previously I ran the furnace self test and the Inducer, the HSI, the Blower low speed & the blower high speed all worked as expected.

Previous problems I had with the heater seemed to be done so I fired up the heater and the inducer the HSI worked the burners were ignited but the blower didn't come on. the fault code was 34 which indicates since all other things are working that the flame sensor, though clean isn't putting out the required voltage.

Fast forward, I stopped working on the heater because the outside temp is now 85-90F. At first the A/C unit seemed to be working, putting out cold air to the registers. Cycle forward a day, the thermostat had turned the system off because the house was cool enough. I manually cranked down the temp in hopes of the A/C commin on but it did not.

I went back out to the furnace and took the proper steps to run a self test. The Inducer turns on, the HSI glows but the blower just hums instead of turning. Is this a possible capicitor problem or is it more likely a blower problem?

Doc Holliday 06-15-2011 02:24 PM

It could be either at this point. If you try and spin the blower wheel (with the power off as if it starts to spin with power and your finger is in there then goodbye finger) and it is hard to spin/does not spin freely meaning acting like the motor bearings are seizing than it's the motor for certain.

The motor should also be extremely hot to the touch if this is the case.

dhigginx 06-15-2011 05:50 PM

The blower wheel spins freely does that mean Capacitor??

Marty S. 06-15-2011 06:30 PM

Why not buy a mutimeter and check the capacitor, motor and control board instead of guessing? All we can do from the computer screen is tell you what to check. From there on it's all you.

dhigginx 06-15-2011 06:40 PM

I have the meter I'm lookin for instruction on what and how to check. Any help given is greatly appreciated.


Marty S. 06-15-2011 06:55 PM

Turn power off, set meter to mfd and check capacitor. Hook cap back up and turn power back on. Set stat for cooling and if motor doesn't start check the leads where they hook up to the control board for correct voltage.
Cap tests bad -replace it
Cap tests good and motor has correct voltage and still won't start then it's the motor.
No high voltage to the motor then it's the control board.

Doc Holliday 06-15-2011 08:01 PM

I do believe he said that the motor was humming which is a good indicatation that it's receiving voltage.

OP, your meter has to have mfd reading capability to check that cap. With the breaker off to the furnace you need to disconnect the two wires from the cap and then check the cap without any wires on it.

There is a number on that cap, something like 5 or 6 or 7.5 mfd and you have to be within a certain range (percentage) of that number on your meter which will also be printed on the cap, something like 5% of 5 mfd and the cap most likely is still good ALTHOUGH there have instances where the cap reads good and it isn't.

So 5% of 5 would be .25 so on a 5 mfd +/-5% run capacitor anything above or below that 5 mfd +/-.25 (so 5.25 on the plus side and 4.75 on the negative side) would be considered bad. If the cap doesn't read at all than it's definitely bad.

If you do not have a meter that reads mfd than that cap is so cheap, $5 to $10 max, you can just get the numbers from it and go buy one and install it and see if your motor works.

Marty S. 06-15-2011 08:38 PM


Originally Posted by Doc Holliday (Post 667990)
I do believe he said that the motor was humming which is a good indicatation that it's receiving voltage.

Dang I read right over that. Sorry Dennis that post came off as a bit gruff,didn't mean to be.

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