A customer reports that a six-month-old furnace stops heating only on very cold nights. What might the technician suspect?

When a heating system behaves differently under various temperature conditions, it's essential to consider components that could be affected by those changes. In this scenario where a furnace stops heating only on very cold nights, the technician might suspect a defective gas valve regulator.

The gas valve regulator controls the flow of gas to the burner, and extreme cold can affect its performance. When temperatures drop significantly, the pressure in the gas line may change, which could hinder the gas valve's ability to provide the correct flow of gas needed for combustion in the furnace. If the regulator fails to open or close properly due to temperature-related issues, the furnace may fail to ignite or stay lit during particularly cold nights.

Other components like the ignition module, heat anticipator setting, and vent fan operation could also contribute to heating issues, but they would be less likely to exhibit the specific symptom of only failing during very cold conditions. A defective ignition module might fail to ignite under any conditions, while problems with the heat anticipator or vent fan operation usually manifest in more consistent heating issues rather than being limited to colder nights.