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Question DetailsAsked on 3/15/2015

Why won't my furnace turn on if my pilot is lit

Pilot is lit power for the furnace isn't working

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2 Answers

0
Votes

Here is a link to a prior similar question with several answers that might be of help -


http://answers.angieslist.com/pilot-l...


I am assuming this is a sudden failure and no gas or electrical repairs or appliance service has been done recently that could have resulted in the gas control valve being turned to Pilot, a main service shut off but not fully turned back on, breaker turned off, etc. I also assume everything else gas and electric in the house is working OK - including that ALL circuits are working, not just half of them which could indicate a loss of one side of your 220V power feed, which is most commonly due to a downed powerline so your neighbors would have about half their circuits out too unless downed wire is just on the line feeding only your house.


Check thermostat is set higher than the current room temp at the thermostat, and that the batteries are not dead. Many units set back to 60 degrees or so if the batteries go dead - some will not work at all with dead batteries. Check also, if your thermostat has a "flame" icon or "Furnace On" indication when it is calling for heat, that the indicator is actually on when thermostat is calling for heat. Try temporarily bumping the desired temp up 10 degrees to see if indicator comes on - if it does, but furnace does not kick on then problem is either thermostat wiring to furnace has disconnected, or a problem in the furnace controls. Also check batteries arenot corroding and have corroded the battery contacts so they arenot conducting electricity.


Of course, also check thrermostat programming hasnot been changed to temps you do not expect, and that the HEAT / AC (or COOL) switch has not been accidentally slid to the AC or COOL position.


Check also that filter (assuming forced air unit) is not plugged or pulled out - some units have pressure differential sensors and filter-present sensors and will not fire if the filter is missing or there is too much resistance across the filter because it is blocked.


To be on safe side, check other gas appliance to be sure working right (stove or dryerif gas) or alternatively make sure the gas valve outside at meter (usually just above ground level on the incoming pipe coming up from ground to the meter) is turned on - usually has a rectangular raised tab on the valve designed to be turned with a wrench, the tab should be alinged with the pipe to be on - see link below for images/photo -


https://www.nwnatural.com/Residential...


If tab on valve is almost perpendicular to the pipe, then your gas is almost turned off and letting just enough through for the pilot to burn. Would be due to some maintenance work or maybe vandalism - call utility before turning on in case they turned off for some reason, though there should be a security seal through the locking ear on the valve to lock it closed and a notice put on your door if they did it, and of course it should have shut the gas completely off, not letting enough through for the pilot to work.


Also check the gas valves at the furnace - the gas shutoff valve outside the furnace (handle aligned with pipe is on, crosswise to pipe is off) usually where the black iron gas pipe leads to the furnace gas controller; and also at the gas control valve inside the furnace where the gas flow is regulated before feeding (usually through tubing) to the furnace pilot and burners. Make sure the internal gas controller is set to ON - burner will not light if on PILOT or START or only partway between - typical appearance here -


http://www.amazon.com/Upgraded-Replac...


May have red pilot hold-to-ignite button like shown, or may light pilot by pushing down and holding the gas control knob till pilot stays lit when released while lighting. gas control valve knob (commonly black, as in this example) commonly has to be pressed down when turning from PILOT to ON or it willnot turn all the way to ON. If this control valve has been monkeyed with recently, it may not have been fully opened so turn back to PILOT (pilot should stay burning OK), then back to ON - usually a 1/4 turn of the valve stem.


Check breaker for the furnace has not tripped. If it has, I recommend NOT turning it back on till the CAUSE of it tripping is found and fixed, because it will likely just trip out againfor the same reason, plus turning power back on without solving the problem may cause further furnace damage if something is shorting out.


Check power switch for furnace itself - commonly located on wall within about 3-4 feet or furnace, usually a regular "light switch" in the wires leading to the furnace - commonly, though not always, where household wiring converts to spiral metal flex conduit leading to the furnace.


If your furnace has any indicator lights, check for them being on. If it is getting power at least one of the indicator lights should be on steady - can be green but sometimes red or amber or white depending on manufacturer. If multiple lights are on or any are flashing, that is usually a coded message indicating the type of failure - call a Heating and A/C technician.


If your thermostat is hooked up with a fan-only setting for the furnace, try setting it to FAN to see if it comes on - that would tell you the furnace is getting power and at least partly working andthat the thermostat is at least connected.


Causes that might not be evident - all of which call for an HVAC technician - main fan failure, exhaust gas blower or exhaust flue damper failure if a high-efficiency furnace with exhaust flue leading horizontally out side of house instead of through the roof (usually has plastic exhaust pipe), failed flame rollout sensor thinking it is sensing a flame rollout (this is probably the microtherm talked about in the referenced prior response), failed duct overheat sensor, or heat exchanger leak detection sensor detecting (or thinking it detects) a heat exchanger leak.

Answered 3 years ago by LCD

0
Votes

My problem is my pilot is lit as long as the knob is hell down but to turn the knob in the on position you have lift up on the knob and turn to the on position that's when the pilot goes out when you lift up on the knob.

Answered 5 months ago by discord1




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