Furnace Question

[Slvrvalk1]

My home furnace is in the garage where my Valkyrie is parked (now Valk related), and it has been doing something different.  After it runs, the fan will shut off and then it will come back on for two or three seconds and then go off.  It has never done this in the past.

Does this sound like something simple that I could take a look at, or should I call a repairman.  I do all of my own work on the Valk (valves, tires, etc.).

Thanks for any help that you can provide.

Dave

[fudgie]

LP or gas?
My bosses furnace did that and has a part on order. He has a button that he pulled out and the fan runs all the time now. Thats the button/switch is is having replaced. Now his furnace dont run at all 

Does it run then shut off or just the fan runs and shuts off? If there is no flame and it shuts off it might be the thermalcouple thingy. I replaced mine twice. Mine is ceramic so it breaks easy. Mine still needs gone through but we have not used it in 2 yrs anyway.

[sandy]

Some of the indoor fans come on by a thermal switch. When the temp comes up in the airbox, the fan comes on. When the furnace shuts down, the fan runs till the airbox temp cools off. It sounds like there's some leftover heat which tells the fan to come back on till the heat is blown into the house.

[Farther]

How old and what type is your furnace.  Some of the newer, high effiency, direct vent models models have a post purge phase they go through.  If yours is older, fuel fired model, I would recommend having it checked out by a qualified tech.

[Hoser]

I have a direct vent furnace in my house, it always does that, puts the extra heat in the house after it shuts off instead of wasting it to the outdoors.  Highly efficient,  I'm told.  Hoser

[Hook#3287]

My hot air gas furnace does that.  Been doing it for 20yrs.  Its to send the left over warm air thru the vents.

[Kep]

I operate my own HVAC business... Sounds like the Fan/Limit control...its about a 3" x 5" box mounted to the face of the furnace and when you remove the cover , has a  round dial with temperature increments and adjustable "pointers" that you set the lower one to the FAN OFF temp. and the next higher one to the FAN ON temp. The third one (if equipped) is the LIMIT setting(don't adjust that one).Normally the  OFF is set at 95degrees  and the ON is set at 120-130 degrees. You could try lowering the OFF temp. and/or raising the ON temp. (try 5 degree increments). These controls have a bi-metal coil in them that over time wears and causes mis-calibration of the actual temperature. If  your furnace has a belt driven fan , you may want to check/replace/adjust the belt..lack of proper air-flow could cause these symptoms also.If you want to PM me I could give you my phone # and I could walk you thru any questions you have.