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 11/17/2014 9:17 PM

Two days ago I removed the furnace and replaced the 12V DC motor. The previous motor was no longer working proper due to bad whindings or bearing. I installed the furnace back into the trailer and connected all required wires and fuel line, making sure that all wire connections are solid and secure. I set the thermostat to 75 degrees and then set the switch to the "ON" position. The furnace ran through its cycle for 15 seconds and then the burner ignited. I then checked and the ducts were blowing nice warm air. I ran the furnace for the afternoon to make sure it was working properly.

It had no issues until the early morning hours around 4am. During the first night I awoke to find the temp had dropped to about 60 degrees. I checked the furnaces and found that the blower was running but without flame ignited, so it was just cold air. I turned the switch to the "OFF" position and waited about 5 minutes. I then set the switch to the "ON position again and the furnace cycled for 15 seconds and ignited and ran fine again for about 6 hours. Then it did the same thing.

It will run fine for some time, approximately 5-6 hours cycling when it is needed to warm up the trailer. It shuts down after reaching the temp set on the thermostat... it will then reignite when the temp falls below. However on occasion it will not ignite after the start-up cycle with the blower.... the fan just keeps blowing with no ignition for flame. I am not sure why this is occurring, but I desperately need to resolve this. We have snow on the ground and I cureently have to remain in the trailer a couple months during this winter until my mothers estate is settled the property sells. Any ideas of what to check and what to replace would be greatly appreciated... it is getting too cold to go without heat at night. :)

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 11/18/2014 10:46 AM

Last night it happened twice...... and I found that I can get it to ignite when it acts up by turning the thermostat down for about 5 seconds and then turning it up again. The furnace will then ignite again and will keep running until it reaches the desired tempurature. It then shuts down and will again re-ignite when needed for a number of hours after. I notices a few minutes ago that while it is cycling down after reaching tempurature, I could hear the flame go out, but it seemed to pulse as if it was trying to burn off any gas that was still in the chanmber. It did this pulse sound of reigniting about 8-10 times and then stopped, and the blower remained to cycle as normal.

The fact it occasionally does not ignite is rather odd to me.

Again... any help would be very useful at this point.

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 11/18/2014 7:50 PM

John - As you're learning, intermittent problems are the most frustrating and difficult to troubleshoot. Except for the unplanned shutdowns every 6 hours, it sounds like everything is working correctly. I'm guessing the problem is the thermostat or the circuitboard it connects to. Because the control voltage is very low, something like a bad connection, made worse as it gets colder, could be the culprit. I'd start with the thermostat and make sure it's clean and all the wires connected securely. Also make sure the connections at the circuitboard are clean and tight. Until this is resolved, an inexpensive electric blanket might be a good investment....just sayin. Good luck - Dave

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 11/18/2014 9:35 PM

Thanks Dave.... but an electric blanket will not do too much here, it would have to be an elexctric sleeping bag!!! I am in Fort Erie Canada directly across from Buffalo NY (I see Buffalo from my window about 1.5 miles form me), and if you have seen the weather on national news it is very cold and a LOT of lake effect snow today.

The furnace has been working pretty much all day today (thank God), and it is about 15 - 20 degrees out there. I think it might have refused to fire once, I don't honestly recall... I'm too tired from waking up every 20 minutes all last night to check on it, so I don't remember if it did have an issue for sure today or not.

I shut off one of the runs for the duct when I reinstalled the furnace but I found another heat register (I didn't know was there), that had something in front of it this afternoon. I was wondering if it is anything like a home furnace that will shut down and not ignite if the heat exchange is getting too hot due to lack of circulation and venting.

I am hoping since I removed the box that was hiding the other duct register and now only having the one in the bed room blocked, that it might work all night.

I am still not sure about the board... it crossed my mind also, but if it was the board it would not likely allow it to run for that long before running into an issue. Something like a cold solder joint will do similar.... but rarely like this (electronics is one of my hobbies).

If it was not getting exactly the correct electrical feed because I also had an oil filled rad heater running on the same circuit, do you think this would be a factor? I know when the electric heater engages I can hear the blower fan drop ever so slightly. Not much, but enough to hear it and the lights also show the difference in power.

The furnace remains running and heating, but I am wondering it at the time of ignition of the furnces, if the other heater is also drawing power if perhaps it is just enough interference to cause an ignition problem. It is not much of a difference in draw on the power.... but as I said the lights dim slightly when it comnes on... so perhaps?

What do you think?

I'll admit this has me stumped... but it staying about 70 degrees in here so far so I'll keep the fingers crossed for the night.

Maybe I'll try to ge tout there tomorrow and do a check on the circuit board.

If you any other might have any other suggestions I am certain willing to try a few things if it keeps up.

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 11/18/2014 10:04 PM

John - Yes, you've touched on a couple more possibilities. Anything that could block the air flow or cause the furnance motor to generate less air flow could negatively affect the sail switch, which controls the gas valve. I doubt one register could make a difference as long as another is open, but anything's possible. The radiator sapping enough power to affect the blower, on the other hand, could make a difference, particularly if your incoming power is on the weak side. Regardless of the incoming power, however, your furnace is powered by your batteries, which also get weaker as they get colder. Are your batteries in good shape? Good luck - Dave

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 11/19/2014 11:39 AM

Hi Dave... the furncae is running on 12V through the converter and hydro being supplied through the house. So the battery is not an issue... but it is in pretty good shape as well, but I have another just incase I needed one.

Last night was a better night... there was no isses at all. It kept the trailer at a nice 70 degrees all night. I am hoping the fact that only 1 duct register was open prior was the problem. out of the 3 duct runs I only had 1 open... then found the second and removed the item blocking it so it has clear flow now. The only one blocked is the bedroom which is not in use, and all seems to be ok so far.

I'm hopeful it remains this way for the winter months or until I am able to sell my mothers estate when I can move back into a home. :)

I appreciate all the helpful suggestions. If this happens again I'll be sure to post it for my thoughts on a cure.


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 11/19/2014 12:01 PM

John - Thanks for the update, glad you may have solved the problem. While it appears the battery isn't the culprit, it could have been. Different converters supply 12v power in different ways. While some may be connected directly to the 12v house wiring, others are not. Instead, they use their charger to pump power into the battery and the battery feeds the house 12v circuits. The advantage of this method is that instead of your 12v devices being fed unfiltered converted 120v AC to12v DC power, the battery supplies pure DC power. In this situation a bad battery could make a difference. Nonetheless, it's now working, so enjoy the good (and warm) times. Good luck - Dave

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