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Author Topic: Furnace operation question  (Read 287 times)

Lowell

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Furnace operation question
« on: October 09, 2017, 06:24:24 PM »
We were camping this past weekend at 9000 ft and it got down to 28 degrees at night.  Although we didn't use the furnace much, we did use it to take the chill off. On the last afternoon and evening, I turned the furnace on for bit and got a little warm so I turned the thermostat down and in a short bit the furnace shut down as expected.  Later that evening, it didn't come back on and I turned the thermostat up higher and higher and it still didn't come on. I turned the furnace switch off and back on again a few times and still no luck so I shut it off and left it.  A couple of hours later before going to bed I decided to try it again and it started right up and continued to operate correctly all evening.

I wondered if anyone had an idea why I had the problem? Is there an overheat switch or breaker that might have reset itself?
Lowell

2005 Cherokee28A TT
pulled by 2009 Dodge 1500 Crew Cab 4X4
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Tempe, Arizona

8Muddypaws

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Re: Furnace operation question
« Reply #1 on: October 09, 2017, 07:17:45 PM »
I would suspect the thermostat and/or the thermostat sensor before anything in the heater itself.  We had a fifthwheel that had the temperature sensor right over one of the floor vents.  That didn't work well until we blocked off that vent.
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Memtb

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Re: Furnace operation question
« Reply #2 on: October 09, 2017, 08:40:23 PM »
   Lowell, It's possible that you have a "high temperature switch" failing. But...that's just a "shot in the dark"!
Todd and Marianne
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Wi1dBill

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Re: Furnace operation question
« Reply #3 on: October 09, 2017, 08:47:48 PM »
Several years ago, one of the neighbors had the service guy out to check out why the furnace wasn't working.    He removed the rugs off of the heater vents.  Everything worked fine then.  Don't know how many vents can be covered before the furnace won't work.


Wi1dBi11

Punomatic

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Re: Furnace operation question
« Reply #4 on: October 09, 2017, 11:11:19 PM »
Several years ago, one of the neighbors had the service guy out to check out why the furnace wasn't working.    He removed the rugs off of the heater vents.  Everything worked fine then.  Don't know how many vents can be covered before the furnace won't work.


Wi1dBi11
The high limit switch failed on our S&B furnace. The tech asked if we keep some vents closed. When I said we did, he told me that restricted airflow will cause the high limit switch to overwork itself. Make sure you have enough vents open and no blockage of the cold air intake.
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Gary RV_Wizard

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Re: Furnace operation question
« Reply #5 on: October 10, 2017, 09:47:58 AM »
The odds of the high-limit switch failing are slim but not zero. However, the high limit switch doesn't even come into play unless the fan runs and the ignition sequence starts.

I can't tell from your description whether the furnace tried to light and failed, or simply didn't try. If the fan came on, it is trying. If not, then either the furnace has no 12v power or the thermostat isn't sending the "heat needed" signal (+12v on a wire to the furnace control board).

You may get some useful help from my Library article on Furnace Troubleshooting: http://www.rvforum.net/miscfiles/Furnace_Trouble-2.pdf
Gary
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John From Detroit

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Re: Furnace operation question
« Reply #6 on: October 10, 2017, 09:53:27 AM »
Normal furnace operation when the Thermostat calls for heat the blower should fire right up The burner fires up a bit later.. If the blower did not start.. I support the T-Stat as the problem.
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Memtb

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Re: Furnace operation question
« Reply #7 on: October 10, 2017, 10:12:10 AM »
     Gary, you are probably correct. I was thinking that if the switch "showed high temp" then it would prevent the "start cycle" from occurring. I know in industry...you can't start equipment until all "trips" are cleared/reset.
Todd and Marianne
Miniature Schnauzers - Sundai, Nellie and Maggie Mae
2007 Dodge Ram 3500,  6.7 Ram 6 speed manual, 4x4
2004 Teton Grand Freedom
2007 Bigfoot Class C

Lowell

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Re: Furnace operation question
« Reply #8 on: October 10, 2017, 11:01:35 AM »
Thanks for the replies.  No, the blower didn't come on. So I'm guessing it must have been a thermostat issue?
Lowell

2005 Cherokee28A TT
pulled by 2009 Dodge 1500 Crew Cab 4X4
KF7YET

Tempe, Arizona

 

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