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Old 06-10-2013, 07:46 PM   #1
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Furnace runs for the first night....then won't start up in the morning?

So I'm stuck with an issue and am about to troubleshoot yet again to fix this problem, but I wanted to see if anyone else could throw in some nuggets of information gold for me....

I went camping on May long and ran the furnace with no issues on my 2006 Forest River Yearling Tent Trailer. It ran all the way through the night, and in the morning I turned it down low to 16C so as not to run my propane and power dry. The next evening, the furnace doesn't work. When the thermostat is turned over to engage the furnace, the blower runs its 20 second cycle to clear the combustion chamber and then turns off. The DSI does not "click" and ignite the burner. I boosted the battery with my truck and that was able to turn over the furnace on the first try and ignite the burners and when I took it off the truck it ran through the night again, but the next day it would not start up again after the burner went out. Long story short, the battery I was using had two broken cells so it would make sense that it had a low voltage issue and was not able to turn the blower to its 75% rpm, not activating the sail switch, etc. Oh and plus the charge (from my multimeter) was showing 11.5 amps during this period.

HOWEVER, after the weekend I replaced the battery with a high quality marine battery and an intelligent charger. Fully charged and ready to go, I took it out again this weekend. First night, no problem. Blower turns over its cycle, burners ignite and we're off to the races. Heat all through the night, and again in the morning I set the thermo to low (not off). Next evening comes around, and NOTHING. Same crap. Blower goes through its cycle and nothing else happens. Multimeter shows a charge of 12.7 amps on the battery. I cycle through numerous times and same cycle happens with no burner ignition. The fix came when I charged the battery to full strength again and, oddly enough, it worked on the second cycle.

I am going to be taking the relay board in to see if its faulty, but I am wondering now if it is a faulty sail switch that isn't getting closed. I just don't understand why it works great for the first night and then craps the bed the next. It makes it really hard to fix things when they work when you test them at home and then they don't work in the field. The wife is not happy.....

Any suggestions?

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Old 06-10-2013, 08:14 PM   #2
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After one night the battery is too low to run the furnace. You might have to go to a 2 battery set up. Or find a way to charge the battery during the day.

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Old 06-10-2013, 08:23 PM   #3
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Are you boondocking?
Or hooked to power (110) when it doesn't function the first night and not the 2nd?

It will most likely always work when hooked on power (110v) at home versus not hooked to power.

Caper has a good point

Get a battery disconnect that allows you to either have one battery on at a time or both batteries on or off and maybe a small solar panel to charge each battery indipendantly during the day light hours when not in use if you are not hooked to power (110v)

I am running two 12v batteries and have the disconnect that allows me to use each battery indipendantly or use both at the same time.
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Old 06-10-2013, 08:51 PM   #4
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After the first night with the new battery it said I had 12.7 amps left on the battery, I would think that it would be more than enough to run. Maybe I'm asking for much, but I would think that the battery would get me through AT LEAST a weekend lol

Having one battery per night for a whole weekend seems silly to run a single tent trailer furnace (not even running any lights or any other draw either). Something just doesn't seem right

Oh and I'm not boondocking (I assume that means hooking up at a powered site?). I'm only using the 12V battery
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Old 06-10-2013, 10:11 PM   #5
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The furnace fan is a power hog...the biggest DC draw on the camper. I think what you're seeing is expected with a single 12V battery.


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Old 06-10-2013, 10:51 PM   #6
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Really? That really sucks lol I honestly would have thought it would last longer than that. I wasn't sure what the amperage draw from a furnace would be, but I imagine it would be the biggest in comparison.

So I have an idea, would a battery booster pack (like the 800A ones from Can Tire) be good enough to start it over every day and just let the fan do the slow draw from there? Just from the previous experience from needing a boost from the truck and it running all night gave me that idea.
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Old 06-10-2013, 11:26 PM   #7
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it don't matter how you get the correct voltage to the furnace as long as you do. You may want to check all the connection both pos and neg to the furnace cause you may be seeing a voltage drop from loose or corroded connections, so the voltage at the furnace under load may be less than the control board and igniter needs.

just a thought
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Old 06-11-2013, 10:10 AM   #8
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Hmm that's a good point. The pos/neg connections to the battery have some corrosion on them, I did clean them off but maybe I'll change them out to ensure they have the best connection possible. Thanks again for your advice Garbonz!
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Old 06-11-2013, 08:11 PM   #9
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Originally Posted by Dave_Monica View Post
The furnace fan is a power hog...the biggest DC draw on the camper. I think what you're seeing is expected with a single 12V battery.

X2 recent experience running the furnace drained the battery each night. We had to run our generator on occasion through the weekend to charge the battery.
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Old 06-11-2013, 08:18 PM   #10
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Watch your light usage.
10 bulbs (5 fixtures) draws the same power as the furnace.


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