Induced Draft Blower Motor Runs Constantly

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Posts: 1054
Joined: Sun Feb 18, 2007 3:24 pm

Sun Feb 18, 2007 3:28 pm

Well my Induced Draft Blower Motor is running constantly.
I gotta Direct Vent Forced Air System model number DGAT070BDC.
I took a quick look at the schematics I am getting that the Centrifugal switch is within the Induced Draft Blower Motor "housing".
My blue wire runs from "TH" on the Ignition Module, through the Centrifugal switch, then to a limit switch and so forth.
The unit still operates fine, other than the Induced Draft Blower motor running constantly.

If I push the switch that powers the unit, that feeds the transformer, and let the Induced Draft Blower Motor stop spinning, then push the main swith back on, the Induced Draft Blower Motor usually stays off. 95% of the time.

If the centrifugal swtich is within the Induced Draft Blower Moter housing, Im guessing I would need a Induced Draft Blower Motor. Or I could take it apart and repair it, seeing as how I have a degree in electronics engineering. So would it be repairable, or would it be wise to just get another motor?
Can the switch be purchased seperately?
However, since I haven't done any tests, I cant say that it is the centrifugal switch for sure.
Thanks.


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Joined: Sun Feb 18, 2007 3:24 pm

Sun Feb 18, 2007 3:29 pm

I believe the switch is a proving switch. It proves to the circuit board that there is a draft going into the combustion chamber and that in turn tells the circuit board it is OK to light off the burner. The motor is running because it is getting a signal from the circuit board telling the motor to run in anticipation of a call for heat.
Usually this motor will not run unless there is a call for heat on most models. I have seen some furnaces run the combustion air as a safety factor when ignition has not been achieved. This prevents a pocket of gas from forming in the combustion chamber and the big bang associated with a delayed ignition. In other words the combustion air fan keeps the combustion clean if there is a problem with ignition.I cannot say if that model of furnace has this feature. I would be more inclined to check the switch out and if it is operating OK I would check the board. Could be a sticking relay on the circuit board.

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Posts: 1054
Joined: Sun Feb 18, 2007 3:24 pm

Sun Feb 18, 2007 3:29 pm

Hi,

Go to below link and scroll down to Booster Relay

#7956-3671 @ $23.56 + $6 shipping. Click on pic

for enlarged view.

It is inside Control Box next to Transformer.

Check that first for problem.

It can be ordered from the link if needed.

Take care and best wishes,
Robert

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Joined: Sun Feb 18, 2007 3:24 pm

Sun Feb 18, 2007 3:30 pm

Hey Robert, thanks again. It was the Booster Relay. I finally got some time to get a better look at the heater. When the Heater turned off and the Induced Draft Blower Motor, I wiggled the Booster Relay, and it clicked and the motor turned off.
So I removed the Booster relay and opened it up and repaired it.
I modified the internal spring to incrase its resistance. And I bent the tang that would be where pin 5 is(however thaere is no pin). But it was mainly an issue with the spring not pulling hard enough to break the contact when the relay would "de-energize".

Again thanks for pointing me in the right direction.

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Posts: 1054
Joined: Sun Feb 18, 2007 3:24 pm

Sun Feb 18, 2007 3:30 pm

Hi,

You're very welcome, glad you got it going.

Take care and best wishes,
Robert

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