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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8327
Experience:  Furnace, A/C and heat pump specialist.
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I have a M1MB 070A BW with draft inducer problems, some due

Customer Question

I have a M1MB 070A BW with draft inducer problems, some due to me. Initially the inducer motor would not shut off, but everything still worked. It was just that after the furnace cycled the draft inducer continued to run, periodically stopping momentarily and then immediately starting back up. Thinking it was a pressure switch problem I pulled the hoses off to see if there was water/debris within, but when i pulled off the hose from the draft inducer motor housing, the nipple came with it, followed by the sound of something falling inside. I glued the nipple back on and connected everything back up, but now it's flashing two flashes indicating the pressure switch is open. Ideas?
JA: Did you check the furnace's filters?
Customer: You couldn't have read what i wrote and responded that quickly, but yes I removed and cleaned them.
JA: Do you plan on doing the work yourself?
Customer: Hopefully. Used to help my father with such while he was alive. I'm no pro though.
JA: Anything else we should know to help you best?
Customer: I'd like to remove the drat inducer housing to see if the inside hose fell off too, as I suspect, so would like instruction on that.
Submitted: 10 months ago.
Category: HVAC
Expert:  airheatman replied 10 months ago.

Pressure switch is stuck open because the inducer is still running.This is going to be a defective control board

Customer: replied 10 months ago.
How do you get that, especially given all the other information I provided? Also, asked for instruction in removing draft inducer housing/fan. Thank you.
Customer: replied 10 months ago.
I'm hearing impaired, don't want to talk.
Expert:  airheatman replied 10 months ago.

You stated inducer motor stays on all the time

You mentioned replacing the pressure switch.The pressure switch has no bearing on telling inducer to run or not.Inducer control pressure switch by pulling a vacuum on it

Water or debris in hoses would effect the pressure switch from closing but have no bearing on when inducer runs

Inducer gets its signal directly from control board

AS for instructions on removing inducer I can provide but will be of no use to you in determining why inducer is running. Again even if a hose were off inducer would not run unless board told it to.

Board should only tell inducer to run during call for heat.As soon as thermostat is satisfied, inducer hould cut off. You have a defective board telling inducer to run when it should not be doing so.

Customer: replied 10 months ago.
Never mind, figured out how to open the housing myself, did so, found tube had fallen into fan, removed and replaced it, temporarily put everything back together, and everything works fine now. Sorry your advice did not work out but thank you for trying.
Expert:  airheatman replied 10 months ago.

No problem Not sure exactly what you did but the tube would have no bearing o the motor getting power to run.Do not rate answer.I will request a refund for you.