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  #1   IP: 71.239.9.201
Old January 2nd, 2009, 09:28 PM
rhopkins rhopkins is offline
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Exclamation tappan furnace problems

i need help. i have a tappon furnace (if anyone needs more info i can look it up) I just changed thermostat cause that was cheap to fix and thought it might be problem, but not. The furnace does not stay consistantly runny. If i turn power or thermostat on/off it will come on and runn and perodically it turns on and runs normally, but problem is thermostat is set at 72 and never runs long enough to reach over 68??? I do not know what to do next, please help!
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  #2   IP: 76.22.81.239
Old January 2nd, 2009, 10:07 PM
suemarkp suemarkp is offline
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Could be a lot of things -- a marginal flame sensor (things the furnace didn't light so it shuts off the gas), a bad limit switch (thinks it is too hot), a real problem (the furnace really is getting too hot, bad gas valve, loose wire, ...).

Does the furnace have any flashing diagnostic lights in it (most likely need to remove the cover and look). Do you have the owners manual? If so, use it to determine what the flashing light means.

One obvious thing to check is the air filter -- is it very dirty? If so, the furnace will overheat and shutdown.

With no flashing light, it will take hands on divide and conquer to determine what subsystem is causing the problem. If you don't know how to do that or have a multimeter and know how to use it, then you need to call an HVAC tech.
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  #3   IP: 71.239.9.201
Old January 3rd, 2009, 06:05 PM
rhopkins rhopkins is offline
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Default furnace

Tappan furnace model# G6RA120C-16 any idea how old this might be? I looked it had four flashed which says ignition failer (check ground) what could cause that? what can i fix? i reset it and now no flashes but as i stated it will work for while and stop! yellow light (flame sensor) also flashes meaning low flame sensoe, i do not know if that is bad or normal??? please help do not have money for tech to come out and fix, thank you!
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  #4   IP: 76.22.81.239
Old January 3rd, 2009, 07:19 PM
suemarkp suemarkp is offline
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Others here with more knowledge may know the age of your furnace and what some of the specific problems and subsystems are. I would expect ignition failure and flame sensor to be related. You have an ingition system to light the gas so it burns. A flame sensor determines when the gas has lit. If the gas does not light (or even if it does, but the flame sensors is defective and thinks it has not lit), the furnace will shut down so as not to fill it with uncombusted gas (which good way to get an explosion).

So some things to fiddle with:

Turn down the furnace for a bit (lower temperature setting on thermostat) and then watch the furnace after someone turns up the thermostat. What is the sequence of events you see and hear? There should be a purge fan that runs for a bit. Then the gas should come on and the ignition system light it. Then, it should keep heating for a bit and the blower fan will come on. Eventually, the flame goes off and a bit later the blower fan turns off. NOTE - Some furnaces have an interlock switch on the front cover so they won't do anything with the front door open. You may need to fool this switch to make it think the door is closed (tape it down, hold it with a clamp, etc). Or, try to observe it without taking the front door off.

The first thing to determine is if the gas is lighting or not (so is it an ignition problem or a flame sensor problem).

If it isn't lighting (could be spark or hot wire ignitor), it could be as simple as a bad connection to the furnace. Some of these ignition sources have only one wire and use the metal furnace as the second conductor. If so, unscrew it from the furnace, clean the contact area with emery cloth, and try start the furnace again. If this didn't help, you may need a new ignitor (and it could be the element of what drives it). It is also possible the gas valve is not letting any gas through and the ignitor could just be trying to light air. You should hear a click and whoosh if gas is getting through.

If it is lighting OK, then see if you can find the flame sensor. This could be optical and need its lens cleaned, or it could be a thermal wire which detects heat from the flames. Sometimes cleaning the wire type with emery cloth will make it work if there is a build up of scale and crud on it. If not, that could be the part to replace.
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  #5   IP: 71.239.9.201
Old January 3rd, 2009, 07:54 PM
rhopkins rhopkins is offline
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it all looks ok that is what i do not understand purge fans goes on electronic ingnitor heats up gas goes on and lights runs for a while sometimes it stays going and some times it will start and stop over and over and then not start up by itself for a while unless i restart by turning off and then on? right now been running fine for hours but this morning woulnt stay run ning for longer than a couple of minutes. so all works at times ?? i can try this but any other ideas? From anyone, thank you for the help!!
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  #6   IP: 108.243.110.4
Old April 14th, 2014, 07:30 AM
imbgdddy1961c imbgdddy1961c is offline
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Default rhopkins

sounds like your flame sensor is failing or just dirty. if you take a piece of sand paper and clean it off it should work.
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