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NT-20seq furnace rpod 172 issue

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Aboopoo View Drop Down
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Post Options Post Options   Quote Aboopoo Quote  Post ReplyReply Direct Link To This Post Topic: NT-20seq furnace rpod 172 issue
    Posted: 16 Oct 2020 at 4:30pm
After having intermittent issues with my furnace I discovered the issue was not the high temperature switch the sales switch or the circuit board. It turns out intermittent firing or flame failure is due to a poor adjustment of the igniter. The igniter gap needs to be 1/8 of an inch and the igniter needs to be adjusted 3/16 of an inch close to The burner. The stock igniter when installed was too high so it would intermittently see the flame and then shut the furnace down. It turns out the igniter is also the flame sensor and requires to be directly in the flame to sense a circuit through the flame to ground. If the sensor is too far away the flame will go out or The gas valve will not even start to allow gas into the unit. It was extremely frustrating as I replaced many items and then bent the igniter closer to the burner and decreased the gap to ground. The unit works excellent now!
For those of you that have intermittent furnace firing or not firing. Do any easy check on the igniter and ensure that the gap to the burner is correct and to ground is correct
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jato View Drop Down
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Post Options Post Options   Quote jato Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2020 at 2:53pm
Thank you !  Writing this down as my furnace is almost 10 years old and gets a heavy workout every year; camp a lot in the spring and fall when temps warrant the use of the furnace.  No other option since we normally boondock where no electric is available.
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'11 model 177
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Jim and Diane by beautiful Torch Lake
"...and you will know the Truth and the Truth will set you free."
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Pod People View Drop Down
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Post Options Post Options   Quote Pod People Quote  Post ReplyReply Direct Link To This Post Posted: 18 Oct 2020 at 8:47am
How did you get to the parts noted for adjustment? Did you have to pull the furnace out?
Thanks
Vann
Vann & Laura 2015 179 R Pod
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Aboopoo View Drop Down
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Post Options Post Options   Quote Aboopoo Quote  Post ReplyReply Direct Link To This Post Posted: 18 Oct 2020 at 6:02pm
The first thing you must do is ensure that your gas is shut off and disconnected from your tank. Then lift the seat where the heater for a good view of the heater.
Remove the front heater grill that is held on with two screws. And looking in from the front you will see where you can put a couple of small wrenches on and disconnect the gas line. The gas line should easily pull out from the box which will allow everything else in the box to slide forward.

I was able to pull the heat exchanger and circuit board straight out the front after taking the diffuser off the front. The diffuser is held on by two screws. Once you take that off you can undo one screw just underneath the high limit switch and then pull the entire insides of the heater straight out the front. This would be the heat exchanger and the circuitboard that is attached to a metal divider. The internal guts including the fan all just slide straight out but make sure that you are also able to other disconnect your wiring or have enough of it to pull through.
By doing this the whole internal guts of the heater was able to sit on the floor and I was able to put a metre on the sale switch and disconnect the wires off the high limit switch to test that for continuity. I was also Able to check all the connections between the circuit board or any terminals. The unit is quite a simple unit once you look at it out on the floor and there’s not much to it. Circuit boards can be easily found on Amazon for quite a bit cheaper than the dealers. It was difficult to find a high limit switch that is rated at 165° as the original seems to be out of stock everywhere. I spoke to a furnace technician that said if you put in a higher limit by 5° or so it’s not a big deal. I put in 170° High limit switch and it hasn’t
Caused any issues but I’m sure some will argue that as it’s a safety and must be exactly rated at 165. Regardless if you can’t find the parts sometimes you have to put others in that will do the trick. At the end of the day with the issues of my furnace sometimes lighting sometimes not lighting sometimes lighting for a little while and then going out, the whole problem boil down to the igniter that from the day it was from the dealer, it was improperly adjusted and had two large gap. Do your research on the Internet and you will see the gap specifications are Regardless if you can’t find the parts sometimes you have to put others in that will do the trick. At the end of the day with the issues of my furnace sometimes lighting sometimes not lighting sometimes lighting for a little while and then going out, the whole problem boils down to the igniter that from the day it was from the dealer, it was improperly adjusted and had two large gap. Do your research on the Internet and you will see the gap specifications To be 1/8 of an inch. Mine was probably a 16th of an inch more which sometimes didn’t allow it to spark. It was also too far from ground which didn’t allow it to see the flame very well. A lot of furnaces use a thermocouple to make sure that The pilots stay on. What this does is measures between the ground and the igniter a resistance. If there’s no flame it does not see resistance and then shut off the gas valve. The flame contains carbon which allows the igniter to Double as a flame sensor.
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Post Options Post Options   Quote Aboopoo Quote  Post ReplyReply Direct Link To This Post Posted: 18 Oct 2020 at 6:09pm
Igniter can be easily accessed from the front of the unit. Just remove the front cover using two screws. You will see the igniter on the left-hand side with a spark wire attached to it. Unplug the spark wire then undo the two screws that hold the ignitor in place. Be careful not to break but looks like an asbestos gasket. Be careful when bending the igniter as it is in porcelain so make sure to use two sets of pliers if bending the wires on the igniter. I only had to move mine in a 16th of an inch and down about an eighth of an inch closer to the burner. Doesn’t take very long to do this and once I put it back together I fired the unit up and it sparked right away. You can then look in the small Mica hole /viewing port and see if it sparks when the unit starts up and see if it also turns red right away and is in the flame. If it’s not in the flame it won’t see it and then it will shut the gas off again. The igniter is also a flame sensor. I believe it uses the carbon in the flame to ground and checks resistance. It’s a safety so if there is no flame your unit doesn’t fill with gas.
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mikeyg2347 View Drop Down
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Post Options Post Options   Quote mikeyg2347 Quote  Post ReplyReply Direct Link To This Post Posted: 21 Oct 2020 at 7:02pm
I had this same issue and posted about it October 11. The lesson here is if your furnace isn't igniting, before you get carried away buying parts and over-thinking the issue, check the spacing of your igniter. I drive a lot of gravel roads and the interior of my trailer vibrates and shakes like mad. That caused the igniter gaps to widen and suddenly my furnace wasn't lighting. Very simple fix to bend it back into position. While I was at it I pulled the entire unit and gave it a good cleaning. In one of the replies to my post there is a link to the furnace manual that is extremely helpful.
Mike
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