My comfortmaker furnace, installed in 1997, started runing very strangely
I have a Honeywell programmable thermostat and have since replaced it and the problem still continues. During the night, when it's in the sleep program (57F from 67F day setting), about three hours after the start of the cycle, the blower fan will start to cycle on and off. The thermostat is not calling for heat but the fan still cycles. If I turn the temp up so it requires heat, the furnace runs normally. If I turn the thermostat from heat to off, the fan stops completely. When I turn the furnace back on, with the sleep temp (57F)on, the fan continues to cycle back on/off. I don't want to leave the furnace on over the night or during the day as I am afraid of burning the fan out because of the constant cycling.
Same type of issue here...
I have the same furnace & recently it's been acting in the same type of manner.
This morning, for example, the thermostat was set to 70 but the inside temp was 65. The thermostat said the furnace was running but it wasn't. I flicked the emergency switch next to the furnace (which has worked in the past) & the furnace fan will kick on, I can see the coil heat up to light the gas, & the gas will turn on. After just a few seconds, the gas will turn off, the coil will come back on & the gas will ignite again. This cycle will repeat 3-4 times & then the furnace will just turn off.
Any help would be great. I hope it's just a switch or sensor somewhere. Thanks in advance!
Found The Answer Rusty!!
I was looking around at other forums & found several people with the same problem; along with a common solution.
I did what they said & my heat is just fine now!!
There is a "flame sensor" in the furnace that is most likely dirty. It senses if there is a flame when the furnace ignites & if it doesn't detect one, it turns off. Same thing mine was doing.
The flame sensor may be dirty, litely sand metal rod.
The flame sensor should be in front of the left side burner with a white wire connected to it.
I removed the sensor (it has a single screw holding it in place) sanded the build-up off it & it's working fine now.
Let me know if this works for you. I'd be interested to find out.
This is not exactly the problem that I am seeing. My furnace is working properly if the time from the last time it ran isn't over an hour or so. That is why when it goes into sleep mode, or lower temp setting the furnace doesn't run until the temp drops below the new lower temp. This can take a few hours. This is when it cycles the blower motor on/off. When I raise the temp, the furnace starts and then run normally. I know the part you are talking about and I have replaced it a couple of years ago. This is something new. It's almost like when the thermostat stops calling for heat, (hour or so) the furnace starts the cycling the blower motor.
Still don't know what is going on.
Sorry about that
Sorry I didn't help you out. If you do discover the problem, please let me know. Being that I have the same furnace, mine most likely will eventually do the same thing!
The trickiest part to any repair to this furnace is to diagnose what is wrong with this unit. Typically, the Flashes through the window panel will give you some clue. If you have any doubt of your abilities, it is always prudent and safe to seek professionally certified service repair persons.
Over the past couple of years, this is what I learned. Please read in entirety first before taking making any decisions or taking any action of any kind. If you smell gas or see electrical sparks at any point, stop immediately and follow your local emergency protocal for gas furnace emergencies.
1. Gas won't ignite therefore no heat is generated despite a reboot. Rebooting sequence is on the label of the unit where temperature is lowered on the thermostat, electrical power is switched off, at the gas valve (http://www.white-rodgers.com/pdfs/04...at_pg_063.pdf), turn gas intake to off position, wait 5 minutes, turn gas intake to on position, switch electrical power to furnace to on, move thermostat to slightly above room temperature.
As soon as the thermostat is set to above room temperature by a 1-4 degrees, the unit should start the induction fan, you should get 3-5 firing sequences by hearing clicks and small trace amounts of natural gas and the heat jets should kick in with the main fan to follow. If the heat jets don't kick in, the chances are your "hot surface igniter" went bad which is what ignites the gas mixture that heats the air output. This can be replaced easily and cheaply if you are handy for under $50 for the part at any well stocked hardware store or from a dealer/service outlet. (http://southsidecontrol.com/acatalog...HSI_1804.html). You should also take a steal wool and try to file down any residue on the gas jet sensor. Both of these parts are located just about the heat jets. The igniter to the right back corner and pointing towards the back of the unit and the sensor towards the front left and pointing downward towards the jet. Make sure when putting the igniter back in, it must be aligned properly with the gas mixture flow, otherwise, misalignment will not cause gases to ignite.
Try the reboot sequence again and the gas should light and you should feel the heat from the jets after the orange glow (heating of the igniter). If not, it's the wrong diagnosis and better call the service man.
2. Same scenario where no heat is generated and the jets won't ignite but the hot surface igniter is glowing orange in the same sequence. The chances are your gas valve went bad and is either not responding with the master board sequencing, the valve in the solenoid is not responding, or it's simply not allowing/pushing the appropriate gas mixture through to the jets. This is a tougher install and requires turning off the gas lead to the furnace after the power down sequence starting with the thermostat (see above). If you are a very good plumber and have reasonable electrical skills, you may want to attempt it, but I called a certified technician because I live in a condo. This way I don't violate any building codes, insurance policy due to faulty maintenance, warranties or simply put, put lives and property in danger.
Good luck to all and may your winters be warm and the cost of home heating be low.
Take care and please be careful. Enjoy the DIY task but most importantly be safe and protect yourself and property. ***Disclaimer: These are simply posts of an unlicensed uncertified and non-professional home owner sharing his experience and should not be taken as professional and legalling binding advice for any and all repairs. Readers of this post is taking matters into his or her own hands and the writer is not liable for any and all damages or consequences as a result.
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