(CBS) — If you’re like a lot of people, you wait until it’s cold before trying to turn on your furnace for the first time.

As CBS 2’s Pamela Jones reports, that can be a huge mistake.

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Blue flame lights up a furnace in suburban Wheeling. When the homeowners fired it up Friday morning, it simply wouldn’t work.

They called for a furnace-repair technician at Abt Electronics. The technician, Daniel Raysby, says it was a relatively easy problem to fix.

He says with a cold snap coming a lot of homeowners are finding furnace problems they didn’t realize they had.

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A common culprit: the sensor that detects a flame.

“Just because people don’t get it cleaned. It builds up carbon, and then we have to come out at 2 o’clock in the morning just to scrape it off,” he says.

He checks air temperature, finds any gas leaks and checks for dirty filters — all common trouble areas. Regular maintenance is a money saver, he says.

Depending on the company, a regularly scheduled service check can cost anywhere from $80 to $120.

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An after-hours emergency or calling during a cold snap will cost you much more potentially.