Locate the reported freezing point
Without opening equipment or moving piping, record the affected section, when the problem appeared, and whether there was no heat, a fault code, or water outside the normal drain path. Note any route through a cold wall, floor, garage, or other unheated area. Take photos from a safe, dry location and include recent work near the furnace.
The room temperature at the thermostat or across the basement is not a measurement of the pipe's coldest location. Ask the technician to inspect and measure the relevant area rather than inferring the cause from the word 'warm.'
Do not disconnect the furnace trap, enlarge openings, reroute tubing, pour antifreeze into it, or add an unapproved heater. If water is near electrical equipment, stay clear and tell the service provider. Do not touch wet controls to continue testing.
Ask for a model-specific drainage check
For example, the Lennox ML296DFVK manual requires downward drainage and routing within conditioned space to avoid freezing. Its alternative provisions are model-specific, not a generic heat-cable recommendation. Lennox example drain and freeze requirements.
Ask whether the installed trap, slope, routing, and final discharge match your model's instructions. If cold air or an intake-related condition is proposed as the cause, ask what observation supports it and whether the vent and combustion-air arrangement also needs correction.
Have the provider explain whether damage or another obstruction remains after thawing, what needs replacing, and how drainage and furnace operation will be checked afterward. Do not repeatedly restart a furnace that is failing because its drainage remains blocked.
Make responsibilities and waiting needs clear
A furnace-related correction may involve building, electrical, or general-plumbing work outside the equipment service scope. Ask who will perform each part, whether it is in the quote, and who confirms the complete result. This dependency does not mean MGI offers general plumbing.
If the furnace is out of service, tell the provider the indoor temperature and available temporary heat. Arrange a warm alternative if the home cannot remain suitable while waiting, and ask an appropriate professional about protecting areas at risk of freezing.
Your next step is a service request that identifies the frozen section and asks for the full installed drainage and relevant air-path checks. Close the issue after the cause and post-correction result are explained, not just after the ice melts.