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12-09-2020, 02:00 PM
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#1
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New Member
Join Date: Feb 2019
Location: Graniteville
Posts: 7
M.O.C. #23443
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Dometic furnace does not shut off
Our 2019 3021 rl has a furnace problem. The furnace turns on and heats as required by the thermostat. The heat shut off but the fan continues to run eventually blowing cold air into the coach. I have to pull the fuse to shut down the furnace. Any suggestions ?
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12-09-2020, 04:24 PM
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#2
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Site Team
Join Date: Jun 2011
Location: Wilsey
Posts: 18,799
M.O.C. #11455
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You have to run the fan on auto when you run the furnace otherwise you will get what you have.
__________________
Dick, Joyce, Diego, Picatso and Gustav
2017 3720 RL, and 2013 HC 343RL
Pullrite Hitch, IS, Disk Brakes, 3rd AC, Winegard Traveler, Bathroom door mod, Dometic 320, couch for desk swap, replaced chairs, sun screens, added awnings, etc.
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12-09-2020, 04:43 PM
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#3
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New Member
Join Date: Feb 2019
Location: Graniteville
Posts: 7
M.O.C. #23443
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Dick:
I had the fan set to auto. The heat pump is operating properly. I am guessing there may be something wrong with the circuit board in the furnace.
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12-09-2020, 08:51 PM
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#4
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Site Team
Join Date: Jun 2011
Location: Wilsey
Posts: 18,799
M.O.C. #11455
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Sounds like the next thing to check.
__________________
Dick, Joyce, Diego, Picatso and Gustav
2017 3720 RL, and 2013 HC 343RL
Pullrite Hitch, IS, Disk Brakes, 3rd AC, Winegard Traveler, Bathroom door mod, Dometic 320, couch for desk swap, replaced chairs, sun screens, added awnings, etc.
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12-10-2020, 07:02 AM
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#5
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Montana Master
Join Date: Dec 2017
Location: Mountain Home
Posts: 839
M.O.C. #20949
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Your furnace should be the Atwood AFMD35 series and the 90 second shutdown relay is incorporated on the ignitor board itself.. Sounds like an issue with the shutdown relay
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12-10-2020, 05:28 PM
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#6
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Montana Master
Join Date: Oct 2012
Location: Box Elder
Posts: 4,702
M.O.C. #12947
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You might instead have a problem with the thermostat that is causing the fan to not shutdown. Might be easier to fix if it is where the problem is.
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Bob & Becky
2012 3402RL
2012 Chevy 2500HD D/A CC 4WD
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12-10-2020, 07:48 PM
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#7
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Montana Fan
Join Date: Feb 2018
Location: Arlington
Posts: 136
M.O.C. #21176
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Mine did that when water got on the circuit board from the rain.
__________________
2011 Volvo 780 485 HP/1750 TQ 13 Speed 32000 lb ET air ride hitch
2016 Montana 3820FK Legacy package
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12-16-2020, 01:59 PM
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#8
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Established Member
Join Date: Oct 2011
Location: VIRGINIA BEACH
Posts: 21
M.O.C. #11864
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I wrote a post that said it is not likely the thermostat but what if the wires got shorted together that says "fan on". Might want to pull the thermostat out and see that the wires are good. I will need to look at the schematic and see what turns the fan on constantly.
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12-16-2020, 02:48 PM
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#9
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Established Member
Join Date: Jul 2019
Location: Bromont
Posts: 13
M.O.C. #24475
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We had the same problem on our 2018 3000RE. First called a mobile RV guy to diagnose the problem. He said it was the circuit board...he said he had one in his truck and would sell it to me for $600.! Almost went with it...! Instead, the next day I called Dometic, explained the situation to them and they agrees to send me a new circuit board for free. Once I received it I took pictures of how it was installed and replaced the board...very easy. Saved $600. and all is good now. My suggestion...call Dometic.
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12-16-2020, 05:14 PM
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#10
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Montana Fan
Join Date: Jun 2020
Location: Liberty Hill
Posts: 139
M.O.C. #26548
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I'm a bit confused and it may be semantics. I have a 2018 3120RL and it has two separate functions. The "heater" setting is the furnace and then a separate setting for "heat pump". One operates via all via propane (furnace) an the other via electric (heat pump) One runs nonstop no matter what temp you set it at like another person said..... it heats and then the fan runs nonstop with whatever air temp is in the air. The other works on the thermostats temperature setting.
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12-17-2020, 04:48 AM
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#11
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Montana Master
Join Date: Oct 2019
Location: Jacksonville
Posts: 2,140
M.O.C. #25165
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jeririgged, If you are saying the fan runs non stop when in Furnace mode, regardless of set temp, then you have a problem. It should run for a short while, approximately 90 seconds, to cool the furnace after set temp is reached and furnace has shut down. If it doesn't shut the fan off after about 90 seconds, it isn't working properly. You may have the same or similar issue as the OP. Check thermostat and also control board on furnace where the shutdown relay is located. A call to Dometic may be in order.
__________________
Robert & Diana McNeal
2019 Montana Legacy 3791RD 20th Anniversary Edition
2014 F350 4x4 6.7L SRW
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12-17-2020, 06:39 AM
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#12
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Montana Fan
Join Date: Feb 2018
Location: Arlington
Posts: 136
M.O.C. #21176
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If you take the outside cover off you will see the circuit board it sets on a plastic shelf and the water collects and shorts it out. The repair shop replace the circuit board. I drained the hot water tank when winterizing water ran down the and got in the furnace and the fan came on. So took the cover off and water had shorted out the circuit again. I used the heat gun and dried it out works ok now.
__________________
2011 Volvo 780 485 HP/1750 TQ 13 Speed 32000 lb ET air ride hitch
2016 Montana 3820FK Legacy package
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12-17-2020, 09:03 AM
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#13
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Montana Master
Join Date: Aug 2020
Location: Keller
Posts: 503
M.O.C. #26851
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One of the posts indicated the furnace was an Atwood, not Dometic. OP needs to verify furnace manufacturer, and call their customer service for help. Furnace fan should shut down after about 90 seconds regardless of manufacturer.
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12-17-2020, 09:04 AM
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#14
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Montana Master
Join Date: Aug 2020
Location: Keller
Posts: 503
M.O.C. #26851
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With regard to furnace fan. Are these single speed fans? Thanks.
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12-18-2020, 03:58 PM
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#15
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Established Member
Join Date: May 2020
Location: Campbell River
Posts: 14
M.O.C. #26255
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Also check your instruction manual. We had a similar situation, called an rv dealer to get it fixed and she said to look at the manual a do a hard restart or reset. Haven't had a problem since. We have a 2012 montana mountaineer so not super hightech.
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12-19-2020, 07:02 AM
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#16
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Montana Master
Join Date: May 2019
Location: Alton
Posts: 2,701
M.O.C. #24086
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Quote:
Originally Posted by Mikelff
One of the posts indicated the furnace was an Atwood, not Dometic. OP needs to verify furnace manufacturer, and call their customer service for help. Furnace fan should shut down after about 90 seconds regardless of manufacturer.
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Atwood was bought out by Dometic. I believe they are still essentially the same.
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12-19-2020, 07:34 AM
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#17
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Montana Master
Join Date: Mar 2020
Location: Lamesa
Posts: 621
M.O.C. #26010
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Quote:
Originally Posted by Daryles
Atwood was bought out by Dometic. I believe they are still essentially the same.
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Ref:
https://www.dometic.com/en-us/us/rebranded/atwood
__________________
Danny and Susan wife of 55 years
2019 Ram Laramie 3500 6.4 4x4 CC 4.10 SRW
2020 Montana High Country 331RL
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