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06-07-2015, 02:44 PM
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#1
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Montana Fan
Join Date: Aug 2013
Location: purvis
Posts: 168
M.O.C. #13723
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Dometric thermostat control is blank
Hi all, I have an issue y'all may be able to help with. I brought the 3750 home today for a quick detail and I discovered that the screen for the Dometric thermostat was blank as well as no power to the fantastic fan control for the front living area.
I have checked all of the fuses in the panel as well as check the voltage at the breakers. Everything seems normal here. Any ideas on what to check next?
Thanks
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06-07-2015, 03:25 PM
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#2
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Montana Master
Join Date: Feb 2012
Location: Lake Gaston
Posts: 8,773
M.O.C. #12156
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GFI check?
__________________
Mike and Lorraine
2002 3655 FL, 2005 3650RK
2010 3665RE, 2015 3910FB
F350 crew cab dually 6.7
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06-07-2015, 03:28 PM
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#3
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Site Team
Join Date: Aug 2007
Location: Omaha
Posts: 6,757
M.O.C. #7560
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LLoyd-- Don't know for sure but check you Ground Fault plugs. There may be one that is tripped and I would guess either in the kitchen or the bathroom but the way some of these rigs are wired one never knows where or what they have wired into the same circuit as the ground faults. Maybe one of the electric experts will be along shortly and either confirm my idea or tell me I'm all wet! LOL Let us know what you find.
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06-07-2015, 03:51 PM
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#4
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Montana Fan
Join Date: Aug 2013
Location: purvis
Posts: 168
M.O.C. #13723
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Retired / Rondo,
The 3750 has 3 gfi protected outlets. One is in the bath which is not resettable, on in the kitchen that is not resettable and one at the entrance to the kitchen. This one is resettable. I tried cycling the breaker as well as tripping and resetting the one outlet. No luck so far.
It almost seems like it is a control power issue. Between the thermostat and fantastic fan control is a bank of switches for the lights in the front living area. These work.
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06-07-2015, 03:55 PM
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#5
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Montana Master
Join Date: Oct 2007
Location: silver creek
Posts: 1,507
M.O.C. #7770
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The fan and most likely the thermostat are 12 volt operated. check your 12v breakers/fuses.
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06-07-2015, 03:59 PM
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#6
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Montana Master
Join Date: May 2011
Location: Hixson
Posts: 3,436
M.O.C. #11397
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Your thermostat and fantastic fan are both 12 volt devices. Nothing to do with GFCI outlets which are 120 Volt outlets.
__________________
2018.5 Montana 3791RD
Full Timers 9/1/2010 through 1/16/2020.
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06-07-2015, 04:07 PM
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#7
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Montana Fan
Join Date: Aug 2013
Location: purvis
Posts: 168
M.O.C. #13723
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All of the fuses in the main control panel is good. I checked these with a meter earlier today.
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06-08-2015, 06:34 AM
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#8
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Montana Fan
Join Date: Aug 2013
Location: purvis
Posts: 168
M.O.C. #13723
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Update:
It appears that a mouse chewed thru the cable going to the thermostat. Easy enough, I pulled the return vent cover and found the control cable from the a/c unit, I disconnected the control cable and connected a new cable to the thermostat. No luck. The thermostat still has a blank display. I contacted my RV dealer and he said there is a 4 amp fuse in the return vent that is probably blown. That sounds simple enough but there is no fuse in the return ducting or on the a/c unit. I am guessing that the low voltage supply to the thermostat is fed from the a/c unit. The voltage for the a/c was good at the breaker so I guess the next step is to go back on top and verify that I have power there.
Any ideas where this mysterious fuse is located?
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06-08-2015, 08:25 AM
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#9
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Montana Master
Join Date: Sep 2013
Location: Pensacola (mail forward service)
Posts: 3,198
M.O.C. #13740
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If you saw mouse damage to the RJ cable that supplies power to the stat as well as the control lines, then that would be an issue. Be aware that while these cables look like what was used for that home telephone...they are not always wired the same...sometimes they flip the wiring order. So measure your cables to make sure wiring is the same. Never heard of a fuse being anywhere BUT in the control box for ac/furnace under one of the small metal covers and as well as main ato fuses in converter panel. Power for remote fantasic fan operation isn't part of this power run. If no power to the leds or power switch there, then there has to be more damaged wires somewhere. Can not see these two issues being connected except by keystone using the same ato fuse for both or mouse damage to different wiring. Out of curiousity...is the fuse on the actual fan still okay? The one time I had the switch panel off the wall, I was surprised to see how big a mess the wiring was back there. John
__________________
2012 F350 6.7 L dually, 2013 3800RE with 6 pt leveling, Sumitomo 17.5" load range h tires, Samsung 18 cu ft residential fridge, 8k Morryde I.S. with disc brakes. Full timing since 2012.
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06-08-2015, 08:43 AM
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#10
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Montana Fan
Join Date: Aug 2013
Location: purvis
Posts: 168
M.O.C. #13723
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John
Good point about the RJ cable. The one I picked up was for telephone services. This may be why I still have no power to the Thermostat.
The fuse on the fan in the front living area is good. I would assume that this fan as well as the one in the bathroom are fed by the same supply. The bathroom fan works fine. I traced the wiring for the front fan as far as I could and it appears to be run towards the main control panel and not the return ducting where the RJ cable is run.
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06-09-2015, 02:24 AM
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#11
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Montana Master
Join Date: Feb 2005
Location: Haysville
Posts: 4,261
M.O.C. #3085
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The cable is not the same as a regular phone extension cable.
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06-09-2015, 02:57 AM
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#12
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Montana Fan
Join Date: Jan 2007
Location: Moab
Posts: 316
M.O.C. #6756
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had to do same repair this winter in Yuma! Phone cable is different and had bad board in front A/C. Yep, mice!
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