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Old 10-14-2009, 07:39 PM   #1
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Draft motor does not turn on


Is anyone familiar with a problem where the draft motor does not turn on, therefore the pilot does not light? When heat is comanded from t stat, nothing happens. I am at my sisters. I have the same furnace. Mine works like this. Heat comanded. Draft motor starts. Ignitor lights. Thermocoupler sees flame and turns ignitor off. Burner lights. Fan turns on and blows heat. I can get draft motor to run by disconnecting one of the in line sensors with red wire connecting all. So I know that it does work. What is my next step. John

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Last edited by simphead; 10-14-2009 at 07:43 PM.
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Old 10-14-2009, 07:47 PM   #2
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Draft motor does not turn on


On the control board is there an LED flashing and if so count the number of flashes. There should be a code chart and post results

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Old 10-14-2009, 08:01 PM   #3
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Draft motor does not turn on


I hope the insult was not for me. This model has no LED on the circuit board. Mine at home does. This circuit board is down in the blower section. The "smart valve" has an LED on it. It goes from dim green to bright green. Flashing slowly. Constant. I am an automotive tech. I am very familiar with flash codes and counting.
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Old 10-14-2009, 08:04 PM   #4
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Draft motor does not turn on


Not insulting you So cut it out.

Just hate typing and make it to the point.

So, go to the furnace and jumper the R & W terminal on the control board. You will also have to push in the safety switch on the furnace when you do this.

I am trying to rule out a faulty thermostat
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Old 10-14-2009, 08:11 PM   #5
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Draft motor does not turn on


Thanks for helping me. I am at home right now. I did jumper white wire to red wire at thermostat. Nothing. I did not have my voltmeter on me. I am bringing it to her house in a m. She has a two story and the upstairs furnace is fine. The problem one is for downstairs. Assuming I have voltage for now, and tried jumpering white to red with no result. What would be my next step.
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Old 10-14-2009, 08:12 PM   #6
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Draft motor does not turn on


I also do not know about the safety switch.
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Old 10-14-2009, 08:17 PM   #7
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Draft motor does not turn on


Jumper at the furnace control board.

I should have said that I am trying to rule out thermostat and wiring from stat to furnace. I have had rodents eat though the wires.

Also keep in mind that jumpering at the furnace will save trips to and from the stat.

When I diag a furnace I turn the stat off and work at the furnace.

With the jumper installed at the furnace lightly tap on the relays you may have one stuck.

Measure voltage from R to C should be 24 Volts AC

If the the voltage is there and OK and lightly tapping on the relays with R/W jumped then I would call it a Control board issue and replace the control board
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Old 10-14-2009, 08:19 PM   #8
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Draft motor does not turn on


Quote:
Originally Posted by simphead View Post
I also do not know about the safety switch.
When you remove the lower panel of the furnace there is a switch that the door closes when installed and opens when the door is removed

OK
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Old 10-14-2009, 08:29 PM   #9
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Draft motor does not turn on


Got it. The safty switch is taped in the closed position from a previous visitor. I will remove that tape when I am finished. Thanks for the diag tips. Question. The green light blinking at the smart valve. Does the blinking let you know that it is OK? Or did something else lead you to the circuit board. Or are we just going in diag order? I could go back to her house now. But if you will be online tomorrow, can I just go back to this thread?
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Old 10-14-2009, 08:42 PM   #10
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Draft motor does not turn on


From you telling me earlier that the LED goes bright dim this what we call a heart beat and tells that the system is fine without faults and waiting for a call of heat, cooling or fan

So if we apply the imputs and outputs to the control board look at it this way

Jumper R/W = Input to control board

and the output would be relay closing causing the inducer motor to operate this causing the pressure switch sencing the inducer is running and so on

Well the inducer will not come on when R/W is jumped and lighty tapping on the relays did not cause the relay to close

Thus faulty control board

Also I come to this conclusion after I would verify that 24 vac is present between R & C

If voltage is not present then I would start diag the transformer

Hope this is not confusing
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Old 10-14-2009, 08:50 PM   #11
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Draft motor does not turn on


Not confusing at all. You are a great teacher. Will you be available tomorrow. I will post either way. Repaired or still not working. Thanks.
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Old 10-14-2009, 08:55 PM   #12
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Draft motor does not turn on


Should be here sometime after 6:30
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Old 10-14-2009, 09:04 PM   #13
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Draft motor does not turn on


Thanks. By the way. I read a lot on the web site today. One guy had mentioned that his blower was running with no burner lit and he thought the breeze aroung the pilot area was a bit too much. This furnace also has a breeze going by the pilot light area. I do know it would not effect the pilot lighting and lighting up the burner. But is that breeze normal when the burmer is lit and the fan turns on. One of the techs reply was a cracked heat exchanger. This house id only three years old. Is that an issue?
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Old 10-14-2009, 09:18 PM   #14
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Draft motor does not turn on


Air is always passing by the pilot.

Air flow from the room through the gas horns into the heat exchanger, through the exchanger and out the flue

If air did not flow the gas could not mix with O2 and combust.

If you might think there is a crack in the exchanger then hire a Pro to check it out. I understand that you are a mechanic but looking for cracks in an exchanger needs a trained pro.

If the furnace is only 3 yrs more than likely its fine. I would get it up and running and talk your sister into buying a CO detector
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Old 10-14-2009, 09:26 PM   #15
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Draft motor does not turn on


Thanks for all. Talkk to you tomorrow. John

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