I have a Carrier Weathermaker 8000 (model # is 58WAV075-101HC). My problem is that every so often (once -twice a week) the air blowing out is cold. I observed the problem to be this... When the furnace igniter attemots to light up 2-3 times, the unit won't fire up and cold air just starts to blow through the vents. If I turn the thermostat to OFF and turn it back on, it works again after a few minutes. Is this something major or expensive to fix, or is it something reasonable? My unit was made in 1993. I am very concerned because it is starting to happen more frequently lately... Please help! I appreciate anyone that can assist me.

Check status light, if present. Do the burners ignite at any point? If you are experiencing brief & frequent ignition trials, try cleaning the flame sensor.

Thanks KC13... I will try it when I get home. Thank you for your help!!

One more bit of info that might help (maybe not)...

My gas furnace doesn't have a lit pilot light. It has an ignitor that glows and starts the fire up when the time is right.

Also, when it does fire up, it runs a full cycle and turns off like normal. It will reignite when the temp drops and run the cycle again. The problem is that once or twice a week the flame won't come back on. The ignitor gets red and the unit tries to fire up, but won't. That is when the unit seems to stop and starts pumping out cold air.

I hope this info helps you understand what I am trying to say. I know it's not easy to diagnose when you can't see it. Again, thanks for your help!!

If you haven't already, try removing & cleaning the main burners. Look closely for webbing it the venturis and/or build-up in the cross-light slots.