lukewarm air

[scttmthsk]

Yesterday I left my furnace off while I was at work. When I got home it was 48 degrees in the house. I usually keep it at 64 when I'm home so that's what I turned it to when I got home from work. It normally will heat up fairly quickly but it it was slow to warm up and never got above 60. I thought I had a door open or something. Then I noticed the air was lukewarm coming out of the vents. It is normally very warm. I hoped I don't need a new furnace! By the way, I know I need to replace my filter.

[how]

A dirty furnace filter might make the furnace lock out the gas on an overheating limit call and just blow room temp air after that. Remove the dirty filter, turn off the power to your furnace for a couple of minutes and then turn the power back.
If the problem continues then the age/brand & model of the furnace would help with the diagnostic's.

[heatseeker]

Is it gas or electric and change the filter.

[Mr. fixit]

So did this fix your issue? Also while you are in there changing the filter I also like to give the furnace a little cleaning and check out anything that could be a future issue.