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HVAC Guru
HVAC Guru, HVAC TECH
Category: HVAC
Satisfied Customers: 14001
Experience:  15yrs in the HVAC industry with certificates and degrees.
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I'm still working on the ducane furnace MPGA100B4B. I

Customer Question

I'm still working on the ducane furnace
MPGA100B4B. I have replaced the pressure switch and repaired the vent pipe that had rusted out. Now when power is applied the furnace calls for heat, then faults out for pressure switch stuck open or closed. I tried putting the old switch back on and get same result. Before removing the inducer motor and switch and repairing the ductwork the motor at least kicked on but now nothing. I did notice the the housing on the motor was warm so I have removed power from the system.
Submitted: 11 months ago.
Category: HVAC
Expert:  HVAC Guru replied 11 months ago.

Hello and thanks for using this service, if you have been waiting do not worry or get upset I am just one of the techs on here and I try to get to as many customers as I can and I just picked up your question now. Please give me time to respond sometimes I get your replies late so there may be a delay in my response.

If the inducer motor is not running on check and see if power is going to it from the board, if not replace the board, nothing else will cause that issue other than a bad control board. If there is power to it from the board then either the inducer is bad or the wiring is broken to the inducer.

We are on the honor system for our time, all I ask is please rate my service using the STAR RATING LINK on your page before you leave. If you are not happy with the service please let me know before leaving a negative rating. This is the only way I am paid or credited through the site for my time. This will also allow you to get directly back to me for FREE follow up questions and tips are greatly appreciated! Thanks

Customer: replied 11 months ago.
I still have yet to test the power going to the inducer motor. It was cycling fine before removing it to replace the duct work and pressure switch so I'm wondering if I may have damaged it in some way. As I mentioned the motor housing was getting warm when trying to start the furnace but it was not turning on.
Expert:  HVAC Guru replied 11 months ago.

You could have damaged the board, it is hard to say 100% you really just need to check if you have power to the inducer motor when it starts a heat cycle first and then go from there.

Customer: replied 11 months ago.
Is it safe to assume that the board supplies 24v to the inducer motor
Customer: replied 11 months ago.
Ok my mistake. 120v it is
Customer: replied 11 months ago.
Power from the board is 122V. I also Ohm'd out the motor at 19-20 Ohms
Customer: replied 11 months ago.
I'm leaning towards the inducer motor however it worked just fine before I took it off last week to replace the vent pipe. I'm going to verify tomorrow that the new screws I used when putting the mounting plate back on are not too long causing interference with the fan.
Customer: replied 11 months ago.
One other question. Is furnace cement required for the new vent pipe parts or is aluminum furnace tape sufficient?
Expert:  HVAC Guru replied 11 months ago.

I just tape them, if you need to get them apart in the future it's a pain. You can glue them as I do on installs but mine are just metal taped.

We are on the honor system for our time, all I ask is please rate my service using the STAR RATING LINK on your page before you leave. If you are not happy with the service please let me know before leaving a negative rating. This is the only way I am paid or credited through the site for my time. This will also allow you to get directly back to me for FREE follow up questions and tips are greatly appreciated! Thanks

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