Harman Accentra: no pressure difference due to failed combustion motor?

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New Member
Jan 2, 2016
Hi. My Harman Accentra insert worked last year. When I tried to turn it on for the first time this year, neither the feed motor nor the ingitor came on. I pulled out the pressure switch and when i create a small negative pressure at the input I can hear the contacts close and then open again when the pressure equalizes (so I think the pressure switch is working).

Another thing I noticed is that in test mode (with the pressure switch bypassed), air blows out the front of the stove (which I think indicates that the distribution blower is good), but the motor that has looks like it has a fan mounted on both sides of it that sits right beside the exhaust duct on the stove (the combustion/exhaust motor?) doesn't come on. Yes, it does not come on in test mode. I suspect that this motor is not working, but I would like to be more confident in my diagnosis before I spend $130 for a new one.

Can anyone please help me understand the following:
1. Should the motor that is mounted via a thumbscrew plate to the exhaust duct (combustion motor?) run when the stove is in test mode?

2. What creates the pressure difference for the stove to operate? I suspect that the motor that is mounted via thumbscrews to the exhaust duct is what creates the pressure difference, but I'm not sure.

3. Any other helpful hints or details of operation of the stove would be greatly appreciated.

4. My Accentra insert must be an older model because the parts breakdown and location is pretty different from the documents that Harman has on their website. Can anyone shed any light on this, please?

Thanks a million.
I'm pretty sure that in test mode everything should cycle and run. Let some of these more knowledgable seasoned folks help you. I'm not real familiar with the Accentra's at all. Check your manual for trouble shooting too.

Welcome also! Try using the search bar above if you haven't already. There are many Accentra people here and Harman gurus in general. I'm still in training. Good Luck. I am sure others will chime in and get you thru your issue.
I believe your all motors, including combustion, should run in test mode. Can you spin it to see if its free ?? If spins free, if you can test it with a volt meter to see if getting power..
If you have the stove out check to see if the Ash fell down into fan cavity and has the fan bound up. I see that alot on initial start up if you have not had the pipe cleaned.
When you turn stove on to ignite the exhaust fan starts, then when the vac switch closes from the exhaust fan pulling air out of stove that starts the auger and igniter. In test mode the exhaust fan has to start and make the vac switch for the auger motor to start.
I would guess that you need to clean vpipe and exhaust fan and that would solve your problem
Also the vac switch controls the neutral side of the igniter and Auger motor, so that is why you get the indicator light even if the motors are not functioning. The circuit board has no idea if there is vacuum in the stove or not it just sends the power out and counts on the vac switch to figure that out on its own.
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