Posted: 1/24/2014 9:32:47 PM EDT
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I'm looking for little help
I was sitting on the couch started feeling a bit cool, check the thermostat,temp is only 66 problem is thermostat is set for 70 OK so the furnace appears to not be working First thing turn up thermo, nothing Next turn fan to on, fan runs, great, I know the blower motor is working. It's late, been very cold, don't want pipes to freeze, last morning was -2, so I run to Wally world buy a couple oil type space heaters, thinking this will buy a little time for either me to fix or call HVAC company during normal business hrs I'm thinking turn HVAC fan on to circulate air in house After turning HVAC fan on instead of auto I notice warn air blowing, Hummmm? My furnace seems to be cycling running only while the fan is in the on position.. Anyone have any ideas what my problem is? Thanks 
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Gas , oil, heat pump ?? Most furnaces have a fan control circuit board in the air handler. I would say your problem most likely is the board. Limit switches can cause this also. You need a tech with a meter to diagnose before you start replacing parts. My money is on the fan control circuit board. I have been out of the business for a long while but you would be surprised how little these things have changed over the years. Could be as simple as a faulty thermostat.
The magic tester will sort it out. |
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You sure its not just running and not able to hold temp? Not uncommon w/ the extreme cold.
More info needed - fuel type, age of furnace, sq footage, good/poorly insulated, etc... Also - is the thermostat actually "on" and functioning, and you feel warm air coming out of the register? Sounds like it could be working. Something very basic to check - make sure you have a good filter and the furnace isn't starving for air - will cause it to shut down Also if it's gas or propane make sure that there isn't ice buildup blocking the exhaust pipe. |
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MY furnace is Natural gas forced air unit, in crawl space, entrance to crawl space is outside
Thermostat is old style basic type Filter is clean just changed it couple weeks ago The roof vent/flu looks clear The furnace seems to work fine with the fan set to the on position, I've always kept it in the auto position until tonight, the house is holding temp running like that I was thinking some sort of sensor, fan control board sounds like could be the issue I do have a multi meter unless I can figure out what to test I'll have to call someone, I'm sure all the local HVAC guys are busy plus its the week end I might have a extra thermostat out in the garage, it would be nice it my problem was that simple Its been real cold lately, my furnace has definitely been getting a work out Funny I thought about a new more efficient furnace last summer but thought one more winter |
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Older furnace? If so, you have a bad fan/limit switch.
If you have heat [burner on] when the fan switch on the stat is on "on" but it does nothing [no blower] when on auto, the burner is shutting down on limit because the blower won't cycle on at the set point. If it's a newer furnace with the blower "time on" controlled by a board, the blower relay is probably toast on it and the board would need to be replaced. What is the make and approximate age of the furnace? |