Chicago (CBS) — The arctic air can really put  the furnace to the test.  And, we’re learning the top there reasons why your furnace may fail.

The furnace at the Gillespie home is humming now, but it was out for hours. Space heaters were strategically placed and towels blocked the draft from the backyard.

“The goal was to keep the first floor warm enough, so we wouldn’t have a plumbing issue,” Becky Beaupre Gillespie said.

Still, it was only a little over 50 degrees Thursday afternoon.

“It was humming along until about 6 o’clock last night, and then it just conked out,” Gillespie said.

When the furnace “conked out”, Gillespie looked for obvious trouble – turning it on and off and checking the circuit breaker.

CBS 2 contacted multiple repairs companies to find out the most common furnace problems they were seeing during this week’s polar plunge. They said the main culprits were dirty filters, air intake or exhaust vents blocked by snow and ice and homeowners’ unrealistic expectations about a furnace’s capacity.

Gillespie’s repairman saw another, more serious problem in her furnace.

“It probably took him less than two minutes to say, ‘your inducer motor’,” she said.

He quickly fixed the problem Thursday afternoon. Gillespie is quick to say that she and her family are doing well compared to others who are suffering in the bitter cold spell.

“We know that there are a lot of people who aren’t so fortunate,” Gillespie said.

Repair companies say to have furnaces regularly checked before the temperature plunges.