What makes a furnace go bad?

Dirty filters: Dirty or clogged air filters reduce airflow, making a furnace work harder to circulate. In some cases, a clogged filter may damage the limit switch, which controls the fan. Wear and tear: Normal wear and tear can cause airflow problems, heat control-related problems or even overheating.

When does the furnace blower turn on and off?

In normal operation, your furnace blower fan should come on 1.5 to 3 minutes after your thermostat calls for heat and should turn off several minutes after the heating cycle ends. Your blower should run constantly until the heating cycle ends.

What is the model of this furnace blower?

You are referring to the draft inducer fan motor, he makes it sound like he is talking about the blower motor fan. and other specialties. what is the model of this furnace? Last edited by Plumber Punky; 02-14-2013, 02:08 PM . Ok, thanks for the replies. The combustion fan (or powered exhaust fan) comes on along with the main blower.

How does the Furnace Fan limit switch work?

Your furnace fan limit switch is basically a control system that determines when the furnace blower assembly should turn on and off. The system uses a “temperature probe” to detect temperature changes inside the heat exchanger (see image below) and turns your blower on and off in response.

How old is the g40uh furnace blower line?

The G40UH line is rather old. Yours is a 3 ton, 90,000btu revision 3 model of 80% efficiency. However, if it is a newer install, this should have an integrated circuit board that has LED error codes. Are there any of those? What is the serial number?

How does the Furnace Fan work during the heating cycle?

The furnace air handler blower FAN goes OFF and then back ON during the heating cycle while the thermostat continues all the time to call for heat, and the BURNER KEEPS RUNNING.