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Have two furnaces, the one under the frig works good and is controlled by zone two or bedroom side of thermostat.  

The other furnace under kitchen cabinet does not appear on zone one of thermostat, so unable to turn on.

Any help?

 

Barry

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@Barry W I had that issue last year, but the other way around.  My under fridge furnace didn't work.  If I remember right, there is a fuse or 2 to check.  The issue mine was having was the sail switch was stuck and needed a little bending to free it up.  Once that was done, mine would light up and burn.  Before doing this, you may want to try to reset your thermostat.  

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On my coach, the furnace requires a contact closure to turn it on.  There are 2 blue wires coming from the furnace going to the air conditioner circuit board on the roof.  Cut those wires, strip them and hold them together to see if the furnace starts.  If it does, purchase a generic thermostat at Lowes such as  a Honeywell Home RTH111B non-programmable Thermostat.  Mount is where you can extend the 2 wires connecting it to the thermostat.  You can use that Thermostat to run the furnace.  Chuck B

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@Barry W I misread your first post about not seeing the furnace on the Tstat.  Can you post pics of what you see?  On mine, you can use either heat pump or furnace, so maybe if one of yours is set to HP, you will not see furnace?  My tstat has an on off slide switch on bottom to turn fully off.  I forget the reset process. 

Found on FB

 

Try resetting your thermostat. 

SYSTEM RESET OF DUO-THERM COMFORT CONTROL:
a. Turn the ON/OFF switch to OFF position.
b. Simultaneously depress and hold the MODE and ZONE push-buttons while turning the ON/OFF switch to ON.  FF should appear in the LCD display until the MODE and ZONE push-buttons are released.

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I googled the reset procedure yesterday and reset the thermostat twice, still have the same problem.

Am thinking will go on roof and check if wireing is still intact.

When on zone 2 (bedroom) when switching between modes, cool, HP, furnace and fan appear.

On zone 1 (living room) just cool, HP, and fan appear furnace does not appear in display.

Hope this explains without pics, but if neccessary will include pics in the future posts

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The air/HP on the roof is a generic unit capable of fitting several applications.  The wiring to it, the switch settings on the circuit board, and the type thermostat used determines how a given application works.  Then there is the flat ribbon cable that ties all the units together.  If they cannot digitally talk to each other, they will not work the way they are designed to work.

You need to make a decision as to what you want to do.  If you want to stay OEM from the factory, good luck.  If you want the system to work properly, you need to make some changes.  Many of the components are no longer available.  The new air/HP units come with new designed circuit boards that Are NOT compatible with what you have now.  Any failure with what you have now requires a very costly complete change out of all associated components.  Then there is the flat ribbon cables that ties the units together so they can communicate with each other.  

We full timed in our coach for 6 years.  In order to keep the DW happy, I had to keep all the systems working the way she was use to being working.  There are not many coach owners left that has the HP/furnace found on our coaches.  Most had the Aqua Hot system.  

I suggest that you get out the manuals for your air/HP units and familiarize yourself with each of the components, how they are wired, the many option settings, to better understand what you are dealing with.   Chuck B

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 Barry ,  is this a recent condition or has it shown up on the thermostat before ?

 Do you still have the original A/Cs ?  If they have been up dated you may need to change a dip switch setting .                                                                             Good luck

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1 hour ago, Ray Davis said:

 Barry ,  is this a recent condition or has it shown up on the thermostat before ?

 Do you still have the original A/Cs ?  If they have been up dated you may need to change a dip switch setting .                                                                             Good luck

This is first time I have checked this furnace to try to use since owning coach for three years.  First trip in cold weather.

The rear AC was replaced fifteen months ago, front AC is original as far as I know.

Where would I find info on t he dip switch settings?

Will do more research

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So , zone 1 is the front and A/C that's where I would check the dip switches 

On the roof remove the A/C cover then on the pass side is the control board , it is accessed by removing a metal cover .

The dip switches are on that board . They are small and delicate so go easy with them . On mine I have a furnace sw 3rd from the bottom .

If your furnace dip sw is off turn it on and do a reset of the thermostat so it will recognize the new setting hopefully that will cure the problem .

Take a picture of the original settings so you can return to those settings if necessary .

BTW there is 120 v up there so be careful .

Edited by Ray Davis
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12 hours ago, Barry W said:

This is first time I have checked this furnace to try to use since owning coach for three years.  First trip in cold weather.

The rear AC was replaced fifteen months ago, front AC is original as far as I know.

Where would I find info on t he dip switch settings?

Will do more research

Is the new unit installed in the rear one that requires the new thermostat or did the installer exchange the circuit board for an older circuit board compatible with the old thermostat? 

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4 hours ago, Bob Nodine said:

Is the new unit installed in the rear one that requires the new thermostat or did the installer exchange the circuit board for an older circuit board compatible with the old thermostat? 

Exchanged circuit board, the zone 2 where the new unit is installed shows the furnace under the fridge. Zone 1 where old unit is does not show furnace that is under the kitchen cabinet.  Have not check the dip switchs on old unit yet will get to that tomorrow.

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 Just a word of caution. We exchanged our AC units and neglected to set the dipswitch for the furnace. When using the furnace in a condition that would require the it to kick on, since we had not flipped the furnace switch, we ended up blowing the freon line and had to replace the unit again!

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Posted (edited)
On 10/6/2020 at 2:29 PM, Ray Davis said:

So , zone 1 is the front and A/C that's where I would check the dip switches 

On the roof remove the A/C cover then on the pass side is the control board , it is accessed by removing a metal cover .

The dip switches are on that board . They are small and delicate so go easy with them . On mine I have a furnace sw 3rd from the bottom .

If your furnace dip sw is off turn it on and do a reset of the thermostat so it will recognize the new setting hopefully that will cure the problem .

Take a picture of the original settings so you can return to those settings if necessary .

BTW there is 120 v up there so be careful .

Climbed on roof removed cover on front AC and what I thought was the opening on pass side to control board.

Found capacitors but no control board with dip switches.  All that was in the opening was part nos. 36,43,& 44

 

This is the model of Duo-Therm 630035.331

20201008_125810.jpg

Screenshot 2020-10-08 14.07.32.png

Edited by Barry W
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 Barry , Your model is a little different , my board is on top under cover # 38 .

 Anyway you do have a control somewhere . I saw in your manual it looks like you have a control box accessed from inside .      https://www.manualslib.com/manual/799601/Dometic-57908-321.html?page=15#manual

  Good luck

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On 10/7/2020 at 2:56 PM, Chuck B said:

 

I do not "spoon feed" people.  I point them in the direction I feel they need to go and let them determine what to do.  Chuck B

Luckily, you are one of a tiny minority on this forum that feel that way.  Most everyone else seems happy to bend over backwards to help their fellow RV owner.

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1 hour ago, Ray Davis said:

 Barry , Your model is a little different , my board is on top under cover # 38 .

 Anyway you do have a control somewhere . I saw in your manual it looks like you have a control box accessed from inside .      https://www.manualslib.com/manual/799601/Dometic-57908-321.html?page=15#manual

  Good luck

Was able to find dip switches from this post, filp furnace on reset thermostat now both furnaces appear in thermo and both work.

Do not know why switch was not right but it is now.  Thanks to everyone that posted help

animated-thank-you-image-0067.gif

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@Barry W

That's great news!   Congrats on a nice victory. 

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15 hours ago, Barry W said:

Was able to find dip switches from this post, filp furnace on reset thermostat now both furnaces appear in thermo and both work.

Do not know why switch was not right but it is now.  Thanks to everyone that posted help

animated-thank-you-image-0067.gif

 

Yeah great news .   Air cond is nice but heat is essential especially when DW is cold .   It sure feel nice when we find a fix , it even feels nice  when we can help .   That dip sw was probably like when it left Monaco and no one bothered to figure it out .   This forum is the best , great members here .                       Almost no bickering 

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