Furnace question

LSpence

This summer, the a/c had a rhythmic sound so a buddy looked at it and said it was the blower motor or housing. Before he could do anything, the sound changed to a roar like a plane overhead. My buddy told me to call in a pro who replaced the blower motor, wheel, and capacitor and cleaned the burners and sensor. It worked a day and now is short cycling. The guy can't come back until tomorrow. Any ideas what could be causing this. I did find a large square headed screw on the floor after he left.

mattmia2

Is the blower turning? is the blower wheel loose on the motor shaft? The square head screws are usually setscrews in a pair that hold the blower wheel to the motor shaft. See if the blower is tight on the shaft(after turning the power off of course).

LSpence

Thanks! I'll try that. Before I shut off the power, thought I'd send a video of what happens when it tries to start along with some photos.

LSpence

LSpence

mattmia2

I have a similar lennox and I had to replace the blower motor a couple years ago because the bearing wore in the vertical plane.

LSpence

I can't seem to post the video. Basically, the unit clicks twice then the burner to the far right has a red glow that goes on then off then on and there is a click like it's trying to start (happens twice) then it shuts off.

mattmia2

That has nothing to do with the blower. Is the gas turned on and is there gas to the house? is the switch on the gas valve on?

EDIT:
Is there a click from the gas valve or is the click only on the control board?

Larry Weingarten

Hi, That square headed screw looks like what would be used to secure the blower wheel to the motor shaft. Not having it snugly in place while powering the motor could easily damage both the motor shaft and blower wheel. 🙀

Yours, Larry

LSpence

LSpence

Mattmia2, yes to the gas questions. I think the click is just coming from the control board but I'm not 100%. Earlier this pm, the hair was blowing upstairs, just short cycling. Now, the blower won't start.

mattmia2

The blower I think will start after 45 seconds or 90 seconds or whatever that control board is set to but it won't heat if the burner isn't firing. The blower just runs on a timer, it starts a certain time after the heat call starts and stops a certain amount of time after the heat call ends. If the burner isn't firing you need to look for power at the gas valve after the click and figure out where it stops if it isn't at the valve. There may be safeties in series with only the valve or a wire may have got unplugged from the control board when it was pulled out to replace the blower motor.

LSpence

@Larry Weingarten, I am hoping the new parts came with a new screw and that was the old one. I think I would have heard it if it was loose. It was quiet until it stopped altogether. I was wondering if something is overheating since it short cycled but ran earlier. @mattmia2, that makes a lot of sense. There's a few things on the floor including an electrical wire connector.

LSpence

https://photos.app.goo.gl/utE3K7D9ZuJhWk9K7

mattmia2

My blower wheel if i recall correctly had 2 setscrews at 90 degrees, maybe one of them didn't get re-installed or was left loose and fell out.

mattmia2

The gas isn't turning on when the control is turning it on, the question is why. You move past the knob on the gas vale too fast to see what position it is in. A picture of the schematic from the door is next to see if there are safeties in series with only the gas valve and not the call for heat.

LSpence

Mattmia2... the gas valve is set to "on." I dnt understand your last sentence because I don't know enough. What's interesting is the guy did say the unit was short-cycling and overheating but then said he had it set to "medium" instead of "medium high." He said once he fixed that everything was okay. I didn't understand what he was referring to.