I notice today that my new furnace will stop after about half hour and start again in a few minutes. The room temperature is 66 and I set it to 70. It took several stop and start before it reaches 70. What could be the reason, too heavy filter or not enough air coming back? The air filter is Honeywell Allergen Plus Pleated FPR 7 Air Filter.
Furnace stop and start continuesly
furnace
Related Solutions
I had the exact same symptoms with my natural gas furnace, and it turned out to be the flame sensor.
It's an L-shaped metal bar (but can also be straight, depending on model) that detects if there are flames actually coming out, and turns off the gas if not. It had a white high-temp wire connecting it to the control board. Taking it out, cleaning it with some steel wool fixed the problem for me.
If yours is like the above, you'll only see the back part of it and the bracket, as the L-shaped end is inside the heating unit.
Note: the below was solved. It was a loose wire between the controller and the gas valve (the white wire on the diagram)
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Best Answer
The filter is only one aspect of an over heating furnace. The diagnosis is as simple as taking its temperature. Get a digital meat thermometer. Take the temperature at the inlet and the outlet of the furnace. All furnaces will have their minimum and maximum heat rise listed on the name plate. In leu of that number 50 degrees is a good middle ground. Subtract the inlet temperature from the outlet temperature. If it is within the specified range you are good. If it is really high like above 150 degrees you are likely tripping the high limit and need more air flow. Open all registers, remove the filter and put the fan to high speed. If the heat seems good and you have an analog thermostat it could be the heat anticipator is not set correctly. Analog thermostats have a small wire or coil of wire mounted near the mercury bulb or the bimetallic spring. It heats up a little to shut the heat off about a quarter to a half degree before the set point so it can glide to a stop. If it is set incorrectly it can shut off several degrees early. With the limited information you have provided those two suggestions are most likely but there could be any number of causes.