Lennox G23 furnace cycles multiple times before reaching set thermostat temp

[jimdavisjr]

I have thought about removing the air filter to see if that makes any difference. It is brand new and should not be causing any clogged air path. But it is something to try.

Besides not enough blower motor output, what else can cause this problem? I've tried all of the things listed above. I don't see any Heat Exchanger issues from a pretty thorough inspection with a flashlight from the top and bottom. I have thought about replacing the primary limit switch ... maybe it is opening too early. But the housing where it is mounted does get too hot to keep my hand on it ... so I figured that it was doing its job. From what I can find on the internet it looks like this limit switch should open at 180 F and then close again at 140 F. I have no idea if this is where it actually activates.

[jimdavisjr]

I also thought about opening up another cold air return not far from the furnace to get more air into the unit. But I am afraid that this would goof up the air flow throughout the entire house. It seems like there should be a more appropriate solution.

[Mr Bill]

Besides not enough blower motor output, what else can cause this problem?.

Wrong motor, or turning in the wrong direction.

[Mr Bill]

Whats with this brown wire? must be just an extra wire.

[Joehvac25]

Limits are there to protect you, they normally aren't the problem. I'd go with mr bill here, maybe it's running backwards or wrong hp.

[jimdavisjr]

The cap is 7.5 mfd.

I am still getting air blowing through the registers. If the motor is turning the wrong direction would that be the case.

Oh, one other thing that I have done. When I inspected the evaporator coils I did not replace the side panel to the A frame. I figured that it might allow more air to travel through the system easily. I did notice an increase in air flow through the registers when I did this. But the system still cycles on/off at about 8-10 minutes before the call for heat ends.

[Mr Bill]

The cap is 7.5 mfd. I am still getting air blowing through the registers. If the motor is turning the wrong direction would that be the case.

Yes you could still get air flow, but not a lot.

[tostaos]

We can not diagnose your problems over the net. For that you need to call out that other technician, as I would not trust the company that replaced the motor after reading your first post. You can not ignore this problem as it will cause more damage to your furnace.

[Mr Bill]

Oh, one other thing that I have done. When I inspected the evaporator coils I did not replace the side panel to the A frame. I figured that it might allow more air to travel through the system easily.

So now you possibly have air bypassing your coil, you sure it was not you who replaced the blower motor?

[Mr Bill]

The cap is 7.5 mfd.

Then it's probably a 1/3 hp motor, I am not a Lennox guy, but most I have changed out have been 3/4 hp on furnaces like yours. Model # would tell us.

[jimdavisjr]

Regarding the loose brown wire ... This ties into a quick connect plug that also has the black and white wires coming from 120V power source. After it plugs into the quick connect on the lower level of the panel there is no wire coming through on the top side of the panel ... only the black and white that connects to power.

There are brown, yellow and blue wires that come off of the motor which are all tied together. This is part of what the HVAC Tech did when replacing the motor.

[54regcab]

What I find interesting is your 1st post where you stated the burners do not shut off when the fan is turned on @ thermostat. Could be a wrong or miswired motor not giving enough air on heat speed. With the way the previous tech left the unit, miswired wouldn't surprise me. Certain miswirings can significantly shorten the life of the motor, I wouldn't recommend leaving it running this way. Agree with others, have a different company come look at the situation.

[Joehvac25]

If its a rescue motor it could be wired wrong or simply on the wrong speed.