No heat and it's cold at night

[moonlitblue]

Hello everyone. We have the good luck to have an 05 Monarch 30PDD on an F53 Chassis. 

Last year the Dometic 13,500 roof AC unit decided it did not like us any longer, and just quit the job.

We replaced it with the Rec Pro Houghton Unit and it seems to work okay, this will be our first real summer season putting it to the test. 

Out problem is the Thermostat no longer controls the heat. I have read all the blogs I could find and watched all the YouTube videos on this problem. People say they upgrade to a basic digital thermostat or rewire the original analog unit (see pictures attached for what we have). I've tried 20 different wiring descriptions on the digital unit and the 5 different ways to rewire the analog unit. Nothing, Nada, Nope, none of the combinations work. 

The new AC is independent of the original system, just need AC run to it and it works with a remote thermostat. 

However we are out for our first trip of the year and we do not have heat.

Does anyone know the solution on how to handle this dilemma, I can't find anything that works here, I can't even find what wires to cross just to make sure the heat works without the thermostat and we are cold at night.

Help?

[BradHend]

First question I would have is if the fan is coming on with demand for heat. 

Can you post the schematic for the unit as well?

[klcdenver]

Which Houghton model have you installed? I have the A3800 and I do not think it will interface with a Dometic thermostat. You have to use the remote or install Houghton wall pad controller.

I suggest you look at previous post under AC, Heating , and Cooling titled Houghton Install/Thermostat Dead. 

[BradHend]

If it came down to it you could always jump the terminals at the unit as needed  

[moonlitblue]

klcdenver, If you read my initial post I wasn't trying to work the AC off the Dometic Thermostat. I have that all sorted out with the remote that came with the Rec Pro unit. I'm trying to get heat. I have read all the previous posts on this subject, here on this helpful website and none of them answer my question. Thanks for the suggestion, I think you missed the question I was asking.

BradHend, no the fan does not come on, nothing with the Atwood Furnace works, nothing at all. So my question to you is, there are six wires, which ones am I jumping to make the heat work?

I appreciate any help related to the question I asked, I'm at a dead end, the analog thermostat should work as a switch and just turn the heat on, HOWEVER, after speaking with Dometic at length, they tell me there is no way to make the Dometic Thermostat work independent of being in a circuit with the Dometic AC unit, that I no longer have.

I don't know what wires I should try to jump, and Dometic offered no help at all besides telling me it wouldn't work any more.

6 hours ago, klcdenver said:

Which Houghton model have you installed? I have the A3800 and I do not think it will interface with a Dometic thermostat. You have to use the remote or install Houghton wall pad controller.

I suggest you look at previous post under AC, Heating , and Cooling titled Houghton Install/Thermostat Dead. 

 

6 hours ago, BradHend said:

If it came down to it you could always jump the terminals at the unit as needed  

 

[BradHend]

What’s the model of this RecPro Houghton unit?

Couple more questions…

You don’t have the remote for it?

The wiring harness you used, is it only 4 wires or the same wires as in the picture you posted of the domestic stat?

[BradHend]

If it’s just 4 wires (yellow,black,green,white), then it is intended to be 2 wires for positive and negative,  and 1 pair for communication. Therefore not able to jump it out unfortunately. 

[Tom Cherry]

The Atwood is looking for a 12 VDC signal.  You will have to go to the Atwood and get the manual and look at the circuit board,  Your thermostat is a bit different from what most folks have here.  Without all the gory details, the majority have the Dometic 5 button Thermostat.  That is a Multiplexed system and there is a “slave controller” on every unit.  The controller is located in the plenum for the 13.5 K and in the rooftop for the 15K.  BUT, these controllers work for Atwood furnaces and AquaHot systems.  

There is a “pair of wires attached to the controller.  That goes directly to the Atwood or the AquaHot unit. When the thermostat is set for furnace and the contacts close, then 12 VDC (positive & negative) is sent to the “input” wires on the Atwood.  As long as there is 12 VDC, the Atwood runs and heat is delivered.  I can’t fell you how the “Fan” is controlled as in Off, Auto or High or Low.  

We have had many folks convert to different AC units.  The successful ones were able to use their 5 Button thermostats for “HEAT ONLY” and the new systems had wireless or whatever controls.

You need to find the prints for the Monarch.  If not, find the install manual for the Atwood and look at the instructions.  One pair of wires should be labeled as “from Thermostat or maybe 12 VDC from Thermostat.  If you are trying to use the old thermostat, the. Download the manual.  There will be a set of instructions. Experimenting with wires and lack of circuit knowledge has been very expensive for many folks and a simple “read the manual” would,have saved them hundreds of dollars as they messed up or damaged several expensive devices or equipment.

[Dr4Film]

Maybe this link will help!

3107904.025_DometicDuoTherm3107541.009-3107541.017-3107546.008AnalogTermostatControlKits_SPL_AMER(en)_2000_01.pdf

[Dave Pumphrey]

On our 2000 Dynasty, there are 2 blue wires at the front A/C unit that trigger the furnace. The same 2 wires are at the furnace, if you just connect them together, the furnace will run. there is no controlling the furnace fan separately, that is controlled by the furnace. You could just connect a simple analog thermostat to those 2 wires.

[BradHend]

@Dave Pumphrey I think the OP has a newer rooftop unit that is both a heat pump and an A/C unit with only a four wire lead that would connect to the appropriate digital thermostat.   From what I can tell, his only other option to run this unit since he doesn’t have the appropriate wall thermostat is to use the remote, which he also doesn’t have.  
I’m sure there’s a way to get his heat to work, but without proper drawings, I’m hesitant to offer advise. 

I don’t believe this is a simple system as in connecting the blue to get the furnace to kick on, there are communications at play. 
 

The manual I found that I think is for his unit only shows 4 wires connecting to the wall unit.  This wall unit is quite intricate in features and options that could not be attained with standard thermostat wiring. 

[moonlitblue]

16 hours ago, BradHend said:

If it’s just 4 wires (yellow,black,green,white), then it is intended to be 2 wires for positive and negative,  and 1 pair for communication. Therefore not able to jump it out unfortunately. 

Brad, there are six wires, please see the pictures of the thermostat I posted at the beginning of this thread. And given how many combinations I've tried over the last few months, I believe you are correct, there is no way to jump it, we will see if anyone else has an F53 Gas Chassis, I'm learning from everyone who has the DP, that the gas coaches were wired very different for the AC/Heat system. As I mentioned before, Dometic told me directly it wasn't going to work, and "Good Luck" trying to make it work. There is not black wire at all in the system, I would think positive and ground should fire it off, but it doesn't.

[BradHend]

So to get this straight…you are replacing the rooftop A/C unit with a combo heat/cool unit and not using the stand alone furnace  that came with the coach?

[moonlitblue]

1 hour ago, Dr4Film said:

Maybe this link will help!

3107904.025_DometicDuoTherm3107541.009-3107541.017-3107546.008AnalogTermostatControlKits_SPL_AMER(en)_2000_01.pdf

Riichard, I appreciate the redirect, I took a look and it talks about the two blue wires to the heat, that I do not have in my feed. Take a look at the photo I posted, there are no blue wires. I think I'm stuck here.

[moonlitblue]

16 minutes ago, BradHend said:

So to get this straight…you are replacing the rooftop A/C unit with a combo heat/cool unit and not using the stand alone furnace  that came with the coach?

Brad, Just to get everyone on the same page. I have an F53 Ford Chassis, so this is not a DP and has none of the systems or controls that the DP coaches have. 

Next I have already removed the single 13,500 Dometic AC unit on the roof that came with the coach and installed a Rec Pro Houghton stand alone roof top 13,500 AC unit that operates off a hand held remote control. The AC works just fine, you control it with the hand held remote unit.

Breaking the original Dometic Penguin unit out of the system has left the thermostat (Picture posted at the beginning of this) useless. It does not work the heat. I'm not trying to operate the AC with it, I have a hand held remote control that came with the Rec Pro unit to operate the AC.

I contacted Dometic about how to make the thermostat operate just the heat and they told me "Good Luck, you can't do that".

I need to make the heat work. There are not blue wires in the system (see the picture at the start of this post) and I have tried wiring the system with a digital Thermostat, with many different wiring combinations from the 30 videos on YouTube, where people have replaced their analog Dometic Thermostat with a digital, none of that works. I bought a new Analog Thermostat and and wired is 10 different ways (again people who "Made it work" on YouTube, and none of them worked. I have checked the fuse, there is power at the fuse. 

Seeing as Dometic told me it wouldn't work after I changed the AC unit out, I'm asking here if anyone has done this and found a work around.

Aparently, different than the 5 button controller that most of you have (again see the picture for what I have), I don't have an Aquahot or zoned heating. I have one Atwood furnace. Dometic tole me that when I disconnected their rooftop air and went to a stand alone unit, I would have eliminated something (they wouldn't tell me what) that makes the entire coach work as a system and I couldn't use the thermostat I have to make the heat work.

I need the heat to work.

[BradHend]

Tony can you please post a picture of the remote that came with your combo unit? All the manuals I’m looking at are able to control both heat and cool with the remote. 

…via the mode button. 

There is also a three minute start delay for the compressor to come on, could be more if it’s colder. 

[moonlitblue]

13 minutes ago, BradHend said:

Tony can you please post a picture of the remote that came with your combo unit? All the manuals I’m looking at are able to control both heat and cool with the remote. 

…via the mode button. 

There is also a three minute start delay for the compressor to come on, could be more if it’s colder. 

Brad at the beginning of this post I put the pictures of the thermostat I have and the wiring associated with it. I don't have a combo unit, not really sure what you are asking. I have a stand alone Rec Pro 13,500 unit on the roof now, that has a remote, which works it just fine. I'm trying to operate the Atwood Furnace that came with the coach from the thermostat on the wall (see pictures at the top of post) There is nothing I have that has a remote to work heat. There is not heat strip in the Rec Pro unit and as I stated the AC works great with the remote that came with it. There is not combo unit?

I'm trying to make the thermostat that came on the wall of the coach (not a diesel coach, not a 5 button thermostat-see pictures at the beginning of the post) work just the Atwood Furnace that came with the coach.

No combo unit, just heat.

[klcdenver]

Did the Dometic you removed have a heat pump also?

[BradHend]

My apologies.  I thought you had replaced with a dual unit.  
So if you jump white and brown at your stat, nothing happens?  There should be 12VDC on that white wire.

Are you able to locate the wiring going from your furnace to your A/C unit? Should be 4 wires.  +12, -12 and two wires that originally would have connected to a relay in your rooftop control board that closes on demand for heat. 
We can reconfigure your wiring there to get this to work. Not for heat/cool,  but it will get you heat for sure.  That’s what’s important right now. 

[BradHend]

What I’m getting at here is as long as you have constant power to your furnace, you can rewire at your stat and A/C unit to open/close the two wires that go to the furnace.  Just make sure your aren’t switching the wrong wires.  The furnace HAS to have an uninterrupted power supply for the startup/cool down sequence. 

You would be wise to isolate all the other wiring on doing this however. 

Other option is manually connect the two wires when required and skip the whole thermostat rewire. 

[Tom Cherry]

OK….at the risk of being a novice, but having learned a lot here and also installed thermostats and upgraded many heating systems for friends.  This would my advice.

Edited post.  See later post.  A line voltage Thermostat is the simplest.  Later post explains how to install and what to trouble shoot.

 

Edited April 3, 2023 by Tom Cherry
More Research... See subsequent post

[Dr4Film]

My link above in a previous post depicts a special control board which no one has mentioned or whether it even exists.

I think that PC control board is the "Missing Link" to getting his heater to work. The 12 VDC needed to fire up the furnace comes from THAT PC control board, NOT from the thermostat wires.

I have attached a PDF file of the wiring diagram for the thermostat he has and the control board that is located somewhere in his coach.

3107904.025_DometicDuoTherm3107541.009-3107541.017-3107546.008AnalogTermostatControlKits_SPL_AMER(en)_2000_01.pdf

[moonlitblue]

I don't want anyone to think I don't appreciate their input greatly. I do. 

After reading everyone's input, and having spoke to Dometic (they were really cryptic, I believe they did no want me to switch from their AC unit) at length, I believe (given the dometic cryptic conversations) that there was a control board in the old AC (wish I knew that before I scrapped that boat anchor) and now after all your valued insight, I either need to put that board back into the system (not sure where or how) and I'll have heat.

Or take the furnace apart and rewire it to a new thermostat?

I have a multimeter and have a mid level skill set, I was trying to avoid taking the Atwood unit apart, with a work around (need that board though?) and if there isn't a dedicated 12V source at the furnace I have to find one.

I knew we should have kept our 5th Wheel 😉

[Tom Cherry]

4 hours ago, moonlitblue said:

I don't want anyone to think I don't appreciate their input greatly. I do. 

After reading everyone's input, and having spoke to Dometic (they were really cryptic, I believe they did no want me to switch from their AC unit) at length, I believe (given the dometic cryptic conversations) that there was a control board in the old AC (wish I knew that before I scrapped that boat anchor) and now after all your valued insight, I either need to put that board back into the system (not sure where or how) and I'll have heat.

Or take the furnace apart and rewire it to a new thermostat?

I have a multimeter and have a mid level skill set, I was trying to avoid taking the Atwood unit apart, with a work around (need that board though?) and if there isn't a dedicated 12V source at the furnace I have to find one.

I knew we should have kept our 5th Wheel 😉

@moonlitblue  Please go back and read my posts as I think I have resolved the issue and can now suggest a fix....which will be easy....and also recommend that you not do any "rewiring" to the Atwood and use the existing wire runs to install a line thermostat and make the system functional.

OK....spent a bit of time trouble shooting and discussing this with one of our experts.  Here is the scenario, based on what has been posted.

Odds are, but we don't know, there was a "controller" inside the 13.5K BTU system.  These are inside the plenum.  The correct way to install a Houghton or any other brand different from the Dometic is to FIRST...read the prints and understand the control circuitry.  The AquaHot and the Atwood Furnace work off a dry set of contacts or "close the circuit" for heat.  That is what the Dometic controller does.  There was a pigtail from the Dometic that had the infamous ""Blue Wires".  it went to a connector, in the plenum about 12" long.  That connector can have any color wires depending on the year, so unless a member has the same exact MH and pulls off the lower cover or air filter housing and looks an tells you the colors, you do NOT know.  

The first thing is to look for a two wire connector....it may have white wires or they may be colored.  That connector then goes directly from the Controller end to the Atwood furnace.  If you chase those wires, then using a paper clip, and jumpering them....the Atwood should run (probably at high fan) and also fire up and give you heat.  IF you have another Dometic, then locate the controller.  if it is a 13.5K, it will be in the plenum.  Richard provided a schematic.  Now, if it is a 15K, the controller will be on the roof.  Look at the blue wires....(or the furnace leads).  

Now, what is needed to fix your system is the line Thermostat that I posted earlier.  You will have to do some testing or wire verification.  If you can download a copy of the manual for the Atwood that you are trying to get to run, there will be a schematic and you will find the two TERMINALS that have the two wires going to the old 13.5K unit.  Then, shorting or jumpering these wires will fire up the Atwood.

The issue that these wires do NOT go back to where the Thermstat is located.  There are terminated inside the old Dometic Plenum and must be found.  There is another pigtail, we believe is there and this is how you salvage the system.  Per your photo, there is probably a 6 wire pigtail.  Whether all 6 wires are used or whatever, all you need to do is locate TWO to salvage.  Look at the wires that were on the old thermostat.  take you choice.  I would NOT use the "Red" or Power or Green or Ground.  That leaves 4 wires.  You only need TWO.  Attach each on to the 2 wire pigtail going to the Atwood.

Now where the hole is where the old thermostat was....use the same two wires.  On the Honeywell Line Thermostat (Amazon), hook either one up to L1 and T1.  It doesn't matter.  This is a Switch leg and not power and not polarized.  When you set the temperature to say 80 Deg and the inside is 75, then the switch will close and L1 and T1 will be connected or close a circuit.  That goes directly back to the new AC Plenum and those two wires are attached to the two that go to the Atwood.  BINGO....you got heat.  if you turn down the thermostat to 70 and it is 75 inside....the switch OPENS and the circuit is broken.  The line thermostat also has a OFF switch (which most line thermostats do not).  So, when you don't need heat or it is storage, the Atwood will not come on if the dial is turned to OFF.

NOW....all the above is based on how the Dometic Controllers work...  So, you need to verify, from the Atwood manual that your furnace simply needs the circuit from two terminals CLOSED.  I downloaded a "typical" ATWOOD installation manual and printed out the schematic.  If you look at yours, the board may be different but if you get you own manual, you should see that the contacts on 2 & 5 are "Thermo".  Polarity is not an issue and Dometic never, as does Aquahot, worry about them....if you took a paper clip and jumpered 2 & 5, odds are....the furnace will start and run.  All the fancy "high and low" fan outputs are not used or connected to the Atwood....it runs at ONE speed.

This is how it works.  Since you don't have the infamous "Control Box" which is a has the "Relay" in it, you would spend $100 for just the board and then have to find an enclosure ($20)....then make sure all the wiring from the thermostat are intact as well as the wiring to the Atwood....then chase the color codes and use your old thermostat...except set it for heat only.  My suggestion is a line thermostat and not having to noodle out where all the wires go the board...

The line thermostat only gives you heat....and that is all you want.  I have installed these and used these and they are robust and reliable and Honeywell is a good name.

I did hide some of my previous posts as there were repeats.  This post clarifies it for you.

Based on your comment about using a VOM and also having some "mid" trouble shooting skills", you should be able to follow my narrative and easily hook this up and make it work.

Good Luck...

Atwood Furnace Wiring Schematic.pdf

[W7BE_Bob]

Are you absolutely sure the unit you bought has a heat pump option? What is the label on the red wire? Is it +7.5V or? 

If all else fails remove all RV wiring, use new temporary wiring and thermostat eliminating all RV and Dometic wiring etc and verify that the heat pump works.