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Author Topic: Duo-Therm Comfort Control stopped showing Furnace Mode  (Read 2558 times)

AtkinsCS

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Duo-Therm Comfort Control stopped showing Furnace Mode
« on: March 11, 2016, 10:00:05 AM »
I have a 2006 Newmar Kountry Star 3507 with a Duo-Therm Comfort Control Center (3109228.001) controlling a Suburban Gas Furnace and two roof mounted AC units (2-zone).  Everything has been working fine until one chilly morning...the Duo-Therm no longer shows a Furnace Mode.  When I cycle through the modes it provides Cooling, Fan, and Off...but No Furnace.  It was working great one minute and then the next the furnace mode is missing  :(  I've checked the furnace fuses, propane, circuit breakers, etc.  The Duo-Therm works, lights up, adjust just as it has in the past except the furnace mode is missing.  Help!

Gary RV_Wizard

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #1 on: March 11, 2016, 12:07:57 PM »
There should be a way to reset the thermostat and that often fixes such problems.

If you have the classic 5-button Duotherm CC, this document may help:
http://bryantrv.com/docs2/docs/ccc5.pdf
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

AtkinsCS

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #2 on: March 12, 2016, 03:20:54 AM »
Thanks Gary. There was a reset in the manual which I performed (got the FF display which reset it to factory specs). Didn't solve the problem though. Hope someone else has experienced this problem and knows a specific fix. Very odd.

Gary RV_Wizard

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #3 on: March 12, 2016, 08:08:52 AM »
The thermostat may be reacting to the status of the zone controller, which is probably located at the a/c unit interface.  Maybe a disconnected wire there, or a faulty board?  I think there are DIP switches in the zone control that indicate whether a furnace is connected or not.

I'm not familiar with that t-stat, though my Atwood Comfort Control System is very similar.
« Last Edit: March 12, 2016, 08:10:56 AM by Gary RV Roamer »
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Sr Fox

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #4 on: March 14, 2016, 09:36:38 AM »
I just replaced my Duotherms last year with thermostat.  I would guess you have a connection problem in the wire that looks like a telephone wire.  Be sure the connection are clean and secure on the thermostat end and the connection at the A/C unit.  Also check the fuse for the furnace.  If there is no power to the Furnace the thermostat may think it is no longer in the system loop.
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AtkinsCS

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #5 on: March 17, 2016, 09:28:16 AM »
Problem solved, so I'm posting my own solution for reference just in case someone else has a similar problem.  When the RV is manufactured and the AC's are installed there are control boards in the AC's that send configuration signals to the Duo-Therm.  These configuration signals, at least in part, are set by DIP switches.  The DIP settings include (but are not limited to) zones (in the case where there is more than one AC Unit) and furnace (can be assigned to a particular zone).  Interestingly enough, the design of the Dometic AC unit installed on this RV, and the physical orientation of the control board makes the "ON" setting of the DIP switch in the up position.  Gravity, road bumps, jostling of any kind can, ever so slightly, cause the DIP switch to drop from the "ON" setting to somewhere between "ON" and "OFF".  In my case, I was parked but walking through the RV (which is very little in terms of jostling). It was nearly imperceptible to the naked eye when I looked at the DIPs.  However, by cycling the DIP from "ON" to "OFF" to back "ON" it reseated itself.  I suspect this will happen again (and probably when I least want it too since I use my RV year round).  A less than qualified mechanic might have diagnosed the control boards as faulty (now beyond end of life and not manufactured) and would have replaced them at a cost of more than $1000 (parts and labor estimate I was given).  Even if the DIP was bad, by having two AC units and a single furnace, I had the option of switching the two AC control boards with one another...only the Zone 1 had a furnace so only Zone 1 control board needed to have the furnace DIP set to "ON".  If I have to reset again, total time to perform this reset is >30min and mechanical/electrical difficulty is low.  In other words, it is easy to do, you just need to know this can happen.  Hope this helps anyone experiencing a similar problem.

Sr Fox

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #6 on: March 17, 2016, 10:21:57 AM »
Thanks for the update.  The contacts on the dip switches may be getting dirty or a bit corroded.  Get some good electronic contact cleaner (not WD40) and spray the switches and move the on and off a number of times. This should clean them up. 
Good luck!
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AtkinsCS

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #7 on: March 17, 2016, 10:50:49 AM »
Thanks Sr Fox...I will do just that.  The DIP was a bit lose feeling as well, kind of mushy in the "ON" position (not a clean click).  I may need to wedge something into the DIP gap to keep it from falling into the "OFF" position again (like a shot of clear silicon that will go in liquid and dry solid.  But I'll clean before doing that.  Thanks again.

therealsimpsons

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #8 on: March 17, 2016, 11:44:44 AM »
I'm wondering if can explain what a DIP switch is (the world of acronyms, I suspect) and point out in your pictures where it is located?
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Sr Fox

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #9 on: March 17, 2016, 12:47:52 PM »
Wiki says:  A DIP switch is a manual electric switch that is packaged with others in a group in a standard dual in-line package (DIP). The term may refer to each individual switch, or to the unit as a whole. This type of switch is designed to be used on a printed circuit board along with other electronic components and is commonly used to customize the behavior of an electronic device for specific situations.

DIP switches are an alternative to jumper blocks. Their main advantages are that they are quicker to change and there are no parts to lose.

The DIP switch with sliding levers was granted US Patent 4012608 in 1976.[1] It was applied for 1974 and was used in 1977 in an ATARI Flipper game.

The acronym is:  dual inline package switch
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AtkinsCS

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #10 on: March 17, 2016, 01:47:02 PM »
Parttymer...Pic 93 shows the big picture AC (Zone 1, Front AC) view with the shroud removed.  Pic 94 shows the circuit board blown up on the right side of Pic 93.  Looking at Pic 94, in the center behind the wires is a red block with a bank of small white switches.  If you look close (HD Pic zoomed) you'll see printed on the circuit board above each switch is what the switch does for this installation (make, model, etc.)  You should see one labeled "Furn..." which is the Furnace setting.  Each switch on a DIP (thanks to Sr Fox for the Wiki Def) is a logical circuit (true/false, on/off).  Notice in the "On" position the DIP is switched "Up" which given the right amount of gravity, potholes, bumps, and jostling, it is possible for it to move down and go from an "On" position to an "Off" position.  This is why my furnace disappeared from the Duo-Therm Comfort Control...the Duo-Therm looks for this signal to determine if a furnace exists or not.  This switch is usually set at the RV's original build and then forgotten...in my case I had to go back and reset it.  From my experience DIPs are a weak point in design when environmental conditions get a bit dynamic (moisture, g-shocks, etc.)

therealsimpsons

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #11 on: March 24, 2016, 10:03:48 AM »
Looking at Pic 94, in the center behind the wires is a red block with a bank of small white switches.  If you look close (HD Pic zoomed) you'll see printed on the circuit board above each switch is what the switch does for this installation (make, model, etc.)  You should see one labeled "Furn..." which is the Furnace setting.

Holy crap! Learn something new every day here!  :) As the old timer's (wait a minute..that's me now!) always say, "this brings on more talk". Why is there a DIP switch that controls the "furnace" on a PCB for the air conditioner?

Thanks for the information, Atkins, and Sr Fox.
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400 HP C9 Cat
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Sr Fox

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #12 on: March 25, 2016, 10:20:03 AM »
The PCB on the first ac is what controls your whole system.  If it was not there it would have to be in the thermostat resulting in more internal wiring. Now the whole think can be controlled with low voltage wiring in the form of a telephone wire.
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israndy

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #13 on: March 26, 2016, 12:28:52 AM »
Problem solved, by cycling the DIP from "ON" to "OFF" to back "ON" it reseated itself.

So jealous. I have this exact issue. It came this way when I got it. I think it never worked as there is NO soot on the front furnace, but LOTS on the back. BUT, I have a sink over my AC unit. A friend has the same RV and had to replace his AC last summer and had to take the entire sink unit out. Arg!

  -Randy

Bobvelabb

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #14 on: October 28, 2017, 09:31:04 PM »
I have two zones and two furnaces zone one shows furnace zone two does not. So are these switches located in the air conditioners or the furnaces?

israndy

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #15 on: October 28, 2017, 10:32:04 PM »
Switch is in the AC unit under the shroud and under the metal cover plate for the control board

  -Randy

Bobvelabb

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #16 on: October 30, 2017, 07:41:41 AM »
Is it under the first air conditioner zone 1 or 2nd zone 2 which is the furnace not showing?

israndy

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #17 on: October 30, 2017, 10:20:37 AM »
The wires for the furnace go directly from the AC that has the switch thrown, so whichever zone the AC isn't showing for will be the one that needs the switch thrown if it's as the above repair.

I STILL have not taken a drill to my grill/sink on the roof to get access to the AC. Probably would be beneficial to try just shorting the furnace leads together to be sure it's NOT the problem before taking the roof apart.

  -Randy

signman501

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #18 on: November 02, 2017, 06:00:31 PM »
Do both the AC's work this on this setup, 2-AC; 1-Furnace. Or does this work from just on AC unit?

israndy

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Re: Duo-Therm Comfort Control stopped showing Furnace Mode
« Reply #19 on: November 14, 2017, 09:39:49 PM »
I have two of each, but if you have two AC and one Furnace than yes, it would only be on one of the two zones.

That is actually how my AC has behaved since I got the new to me RV two years ago. Two zones, but I could only select Furnace Mode in one of the zones. Today I unburied the roof AC, it's mounted under a grill area with sink that I had to disassemble, and even then I had to destroy the shroud in order to get into the AC.

The good news is that the switch appears to have been set incorrectly at the factory  >:(, probably living in Florida no one noticed that the furnace wasn't working. Also explains the number of dead frogs I have found in various locations around the RV including inside this AC unit.

I flipped the dip switch inside the AC and ran downstairs to test and immediately the furnace was showing up in the zone it had been missing from.

The bad news is that the furnace is still not responding, and now I need to buy a new shroud for my Dometic Penguin 15000, I am also curious if these AC units have heat strips, guess the easiest way to find out is to flip the dip switch and try it.

  -Randy

 

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