Lennox , model G23Q3/4-100-5

Problems related to residential installations.

Moderator: juster

Post Reply
Posts: 1
Joined: Sun Jun 18, 2017 11:32 am

Lennox , model G23Q3/4-100-5

Post by kzumblev » Sun Jun 18, 2017 11:37 am

Hello, I have a Lennox unit, model G23Q3/4-100-5 which is about 12-15 years old. Recently, I noticed that my blower fan does not produced enough CFM. The space temperature remains the same and because of that the condensing unit outside is continuously working. If I turned off the AC unit for a while and turn it on again the fan would produce sufficient CFM for a couple of hours. Then it would gradually slow down its speed and gradually decrease the flow rate until the flow became almost unnoticeable.I do not understand very well the electrical part of the system, however I checked the Amps during fan normal operation and during fan slow speed (when the problem already occurred). The Amps were approximately 4.85 Amp and 2.2 Amp respectively. I also checked the transformer voltage and the voltage on the low voltage side were 27 V and on the High V side 123 V. Visually the capacitor seems to be ok. I replaced it couple of years ago.
I am not sure if this is an electric motor issue or it's a control issue. Can someone assist? Thank you for your time!

Most Valued Contributor
Posts: 1019
Joined: Sat Jun 18, 2011 11:26 am

- Lennox , model G23Q3/4-100-5

Post by Freon » Mon Jun 26, 2017 9:12 am

Here's one test you can try. Turn off the power to the air handler. At the control board, jump the R (24 votl AC) termminal to the G (fan) terminal. Turn on the power. See if the blower runs at a constant speed as you would expect. You are bypassing the control circuit and the thermostat so any motor deviations from normal will most likely be a motor issue.

Post Reply