DENVER (KDVR) — With cold nights ahead, heating companies are telling the Problem Solvers their phones are ringing off the hook with people saying their furnaces are not working properly.

And it turns out that there may be a few steps you can take now to make sure your heating system keeps you warm tonight.

On Friday, technician Brian Cheever was in an Aurora neighborhood preparing to check a home’s furnace.

Cheever works for Plumbline Services of Centennial. He said he was up until 2 a.m. Friday answering calls from customers without heat.

Todd Ryan also works for Plumbline as an HVAC service manager. He said hundreds of people have been calling.

“The biggest thing is people are saying no heat, so have a lot of furnaces that are blowing cold air or no heat at all,” Ryan said.

Furnace not working? Check these simple things

One of the biggest problems techs are seeing is something you could fix yourself.

“A dirty filter is the biggest factor in having no heat that we have right now,” Ryan added.

That’s right: Changing your filter could get the system working again.

Simple maintenance could also help stave off bigger problems down the road. That’s especially true when it comes to tiny flame sensors that can collect dust.

“It could cause the burners to cycle on and off and could potentially lock out where it just blows cold air, because it’s going to overheat itself and there are safety switches that are designed to keep it from overheating,” Ryan said.

Many heating and air conditioning companies expect to get even busier as the winter season gets closer, even though it feels like the season is already here.

Bottom line: Get furnaces checked sooner than later.