Blower dropping out mid cycle.

xylie6

Hello All.

Not sure how it works, but I found a post that was having the exact issue I am asking about.

https://forum.heatinghelp.com/discussion/167543/circulating-blower-motor-cutting-out-mid-cycle

Seems like the post is closed though.

It's not clear what, if anything fixed the issue. I'm gonna guess the flame sensor did some good.

Mine is the same issue. The furnace calls for heat normally, normal induced draft, GV opens, blower starts then stops mid cycle. The gas stays on until the limit cuts out the valve.
It doesn't seem to be the blower itself, because I can switch from auto to on and it works OK (single speed blower), but the gas never shuts off so I just cycle it with the T-stat for now. I have a new control board on the way.

Any ideas would be appreciated.

Steve.

mikeapolis

Is it a high limit switch that’s shutting the system down.
Are you getting fault codes?
What’s the furnace make and model?
Thanks

JUGHNE

Will the tstat reliably shut off the gas valve or not?

A new board may fix the blower problem.
If you look on the back of the old one you may see burn spots from bad solder joints on the heating speed relay.......not repairable....the overheating is probably inside the small relay and conducting the heat out of the contact pins melting the solder.

xylie6

Thanks for the fast responses,
Its an older furnace. Armstrong SX80, No codes. I was watching it last night and got more and more worried as the flame was on, but no blower coming on. The high limit opened up and shut the GV down. I then got the idea to just turn the fan to on and cycle with the thermostat. The new board is due Mon. so I'll see how that goes. Will post back.

mikeapolis

If you’re able, take a look at the heat exchanger or have a technician out to check for any stresses.
Good luck with the board swap out.

xylie6

Hello all.

I had a local contractor out yesterday. Furnace is working now. It turned out to be the blower capacitor. Seems it was working somewhat, but not enough. It was really tough to get to also, Located way in the back corner. Kind of a poor design. Anyway, that was it.

Thanks.
Steve.

mikeapolis

I knew it! I was going to ask about that. Oh well, glad it's working again.