New Dometic ACs and Stat but now no heat in bathroom

[Pduggs]

We replaced all three AC units with HP and had new Dometic CCC II thermostat installed.
 

Our Squire has the fully enclosed bathroom with Aqua-Hot heat register under the vanity. Intellitect button on bath wall “AQ-Hot Blower” turns on blower for heat. It worked well BEFORE the ACs and stat were installed. 
 

Installation was done by the Mortorcoach Store in Bradenton, FL in January. I took it back to fix this problem two weeks ago and thought it was fixed. AQ Blower wasn’t working at all after initial install and tech determined it was a bad ground. He fixed at no additional cost but now that it’s cool this morning, we realize it isn’t offering heat. It’s blowing cold air at very low fan speed.
 

I’ve played with the zones and modes on the thermostat to avail. Anyone have any suggestions?

 

[vito.a]

The bathroom heat exchanger only works when the adjacent zone next to it (hallway) is on and blowing air and of course the bath heat switch is on..  

[Frank McElroy]

You have a 4th zone hidden controller.  It is likely in a wall near the thermostat.  Since you replaced all 3 AC units, did you also replace the zone 4 control circuit board with a new one?  Did your thermostat see 4 zones before and now it sees only 3 zones?

[det944]

 Vito is correct. My 2006 Dynasty bathroom blower is activated by the hallway thermostat by the bedroom. This is zone 2 on the thermostat. In order for that bath room blower to run the Aqua hot switch in the bath room must be on, and the thermostat for zone 2 needs to be calling for heat. This should result in the hall blower and bathroom blower activation. My config does not show a Zone 4.

on the thermostat.

[Frank McElroy]

37 minutes ago, det944 said:

 Vito is correct. My 2006 Dynasty bathroom blower is activated by the hallway thermostat by the bedroom. This is zone 2 on the thermostat. In order for that bath room blower to run the Aqua hot switch in the bath room must be on, and the thermostat for zone 2 needs to be calling for heat. This should result in the hall blower and bathroom blower activation. My config does not show a Zone 4.

on the thermostat.

That is correct for 2006 model year Dynasty.  In 2008, they went with a single 5 button 4 zone thermostat.

[det944]

Thanks Frank, still trying to understand these functions.

[Pduggs]

6 hours ago, Frank McElroy said:

You have a 4th zone hidden controller.  It is likely in a wall near the thermostat.  Since you replaced all 3 AC units, did you also replace the zone 4 control circuit board with a new one?  Did your thermostat see 4 zones before and now it sees only 3 zones?

Thanks Frank. I’m unaware of this. You’d think the tech at The Motorcoach Store would know this. No zone 4 control circuit board was replaced. My old stat did have four zones. I have four zones on the new one, but the fourth zone is inactive. Any ideas how I can fix this?

Hey guys if I’m trying to heat my bathroom wouldn’t you think I’d have the other zones on too?  Lol. Of course all my other zones are on, but the bathroom isn’t offering heat. 
 

[Frank McElroy]

11 minutes ago, Pduggs said:

Thanks Frank. I’m unaware of this. You’d think the tech at The Motorcoach Store would know this. No zone 4 control circuit board was replaced. My old stat did have four zones. I have four zones on the new one, but the fourth zone is inactive. Any ideas how I can fix this?

Hey guys if I’m trying to heat my bathroom wouldn’t you think I’d have the other zones on too?  Lol. Of course all my other zones are on, but the bathroom isn’t offering heat. 
 

Yes, I suspected that they didn't replace the 4th zone control board.  The old original board is not talking to the new circuit control boards in your new units.  In effect they need to replace the old circuit board with the same electronic board that is in your new AC units.  The manufacturer should have that specialty option just like Dometic did.

Your 4th zone control board could be hidden in a wall almost anywhere but it will likely be in the wall behind the thermostat.  If your thermostat is mounted on a wall with a cabinet behind it, that cabinet will likely have a side interior wall that unscrews and the control circuit board is mounted behind that panel.

[Johnny Mo]

I had the same issue with an 2009 Dynasty, I found the 4th zone control board behind the mid ship television.

[Pduggs]

30 minutes ago, Frank McElroy said:

Yes, I suspected that they didn't replace the 4th zone control board.  The old original board is not talking to the new circuit control boards in your new units.  In effect they need to replace the old circuit board with the same electronic board that is in your new AC units.  The manufacturer should have that specialty option just like Dometic did.

Your 4th zone control board could be hidden in a wall almost anywhere but it will likely be in the wall behind the thermostat.  If your thermostat is mounted on a wall with a cabinet behind it, that cabinet will likely have a side interior wall that unscrews and the control circuit board is mounted behind that panel.

Wow Frank. You are amazing. I was just now looking for the board and found this a short distance from the thermostat. Lots of cut wires. Not sure if that was done by the shop. 
 

[Frank McElroy]

Those cut wires would go to the AC compressor and sensors which you don't have on zone 4.  The only thing zone 4 connects to is the remote temperature sensor, the aquahot control board and the data cable to the roof AC data port and maybe +12 VDC and ground.  If you look at my picture, you will also see cut wires.

The two blue wires on top go to the aquahot control board.  I also see data cables on the bottom - most likely for the remote temp sensor and data to one of the roof AC units.

[Pduggs]

Okay. How do I solve this problem? Call Dometic and buy the circuit board???  Is it a simple install. Or take coach back to dealer who should have known how to fix it?

[Frank McElroy]

The dealer should be able to replace that old hidden board with a new one compatible with the new AC units.

[Pduggs]

N

3 minutes ago, Frank McElroy said:

The dealer should be able to replace that old hidden board with a new one compatible with the new AC units.

Thanks. 

[Jdw12345]

That’s for starting this thread Pduggs.

I realize that I’m not helping but I have the same issue with my 2005. Previous owner installed a new hp/ac in the main salon with the new style thermostat a month before our purchase and kept the old hp/ac and old style thermostat in rear bedroom, the fan doesn’t not come on under the vanity in the (I call it the shower room) shower room, the heat exchanger does seem to get hot but no fan and the heat exchanger does get hot and blow hot air in the commode room when the switch in the commode room is turned on but cools down after a bit, I assuming do to lack of boiler fluid circulation. 
 I also noticed my wet bay heater seems to come on when the thermostat in the bedroom is on furnace mode. 
 

 We’re not home now so I can’t experiment but will continue to read the thread, if anyone directs a remedy my way and I don’t answer for a week I’m not ignoring you, we’re just not at home we’re the coach is parked!

 

 Thanks in advance!

[Frank McElroy]

1 hour ago, Pduggs said:

N

Thanks. 

Be sure to take a picture of those dip switch settings on the old control unit just in case. 

The dealer will need to configure them for zone 4 heat on the new board and reset the thermostat so it sees zone 4.  That should fix the problem.

[Pduggs]

14 hours ago, Jdw12345 said:

That’s for starting this thread Pduggs.

I realize that I’m not helping but I have the same issue with my 2005. Previous owner installed a new hp/ac in the main salon with the new style thermostat a month before our purchase and kept the old hp/ac and old style thermostat in rear bedroom, the fan doesn’t not come on under the vanity in the (I call it the shower room) shower room, the heat exchanger does seem to get hot but no fan and the heat exchanger does get hot and blow hot air in the commode room when the switch in the commode room is turned on but cools down after a bit, I assuming do to lack of boiler fluid circulation. 
 I also noticed my wet bay heater seems to come on when the thermostat in the bedroom is on furnace mode. 
 

 We’re not home now so I can’t experiment but will continue to read the thread, if anyone directs a remedy my way and I don’t answer for a week I’m not ignoring you, we’re just not at home we’re the coach is parked!

 

 Thanks in advance!

Thanks for your post. I now need to check my heat register in my wet bay. I don’t know if it’s heating. 
 

Hey Frank, do you know if the wet bay is also heated by zone 4, like my bathroom register is?

[Frank McElroy]

1 hour ago, Pduggs said:

Hey Frank, do you know if the wet bay is also heated by zone 4, like my bathroom register is?

There are 3 circulation pumps and 5 available aquahot heating zones.  The bay heating zone is a separate zone but it shares the same circulation pump as the bath zone.  The front aquahot zone uses a separate circulation pump as does the bedroom zone. 

So, if the bay calls for heat only the bay heater fan will run.  The bath heat exchangers would get hot but those fans won't run unless the bath zone calls for heat.  Also, the zone numbers on the thermostat don't match the aquahot heating zone numbers.  This confuses a lot of folks.  If you want to see which zones feed the aquahot zones look at your wiring diagram. 

Keep in mind that in a 3 AC setup the center AC unit does not have an Aquahot heating zone.  Also, for the thermostat to work properly, all AC units must be on zones before adding an Aquahot heat only zone.

Hope this helps.

[justdoingit@att.net]

I think the new 10 button see’s zone 4 board for the bathroom heat, but isn’t comparable with the 10 button thermostat.

The hard part is finding where Monaco put the board, there has been some discussions on this subject before. Need to find it and change it out to a new board.  

[Pduggs]

I contacted the RV dealer. They need a part number for the replacement board. I guess I have to locate that myself. I’ll call Dometic and see if they can help. 
 

[Pduggs]

On 3/16/2023 at 11:56 AM, Frank McElroy said:

There are 3 circulation pumps and 5 available aquahot heating zones.  The bay heating zone is a separate zone but it shares the same circulation pump as the bath zone.  The front aquahot zone uses a separate circulation pump as does the bedroom zone. 

So, if the bay calls for heat only the bay heater fan will run.  The bath heat exchangers would get hot but those fans won't run unless the bath zone calls for heat.  Also, the zone numbers on the thermostat don't match the aquahot heating zone numbers.  This confuses a lot of folks.  If you want to see which zones feed the aquahot zones look at your wiring diagram. 

Keep in mind that in a 3 AC setup the center AC unit does not have an Aquahot heating zone.  Also, for the thermostat to work properly, all AC units must be on zones before adding an Aquahot heat only zone.

Hope this helps.

Hey Frank, I called Dometic and they told me the 4th zone circuit board you thought was the culprit plays no part in controlling the Aqua-Hot with the new AC units. The Dometic tech told me an RJ-11 cable should run from the Aqua-Hot to one of the AC units specifically for the bathroom heat. Since I have heat in zone 1 and 2 (front and rear) I’m guessing the tech at The Motorcoach Store failed to connect this cable or failed to set the dip switch at my middle AC unit. 

I’m going to have to fix this myself, since the dealer seems incapable and they have no open appointments until after we leave Florida. So, I plan to pull the shrouds and see if an RJ-11 cable is connected and dip switch set to the closed position.  I’m guessing I should have one RJ-11 cable connected at each of my AC units. I’m told I’ll have to do a reset of the thermostat after any change in the dip switch settings. 

Do you think this makes sense?

[Frank McElroy]

49 minutes ago, Pduggs said:

Hey Frank, I called Dometic and they told me the 4th zone circuit board you thought was the culprit plays no part in controlling the Aqua-Hot with the new AC units. The Dometic tech told me an RJ-11 cable should run from the Aqua-Hot to one of the AC units specifically for the bathroom heat. Since I have heat in zone 1 and 2 (front and rear) I’m guessing the tech at The Motorcoach Store failed to connect this cable or failed to set the dip switch at my middle AC unit. 

I’m going to have to fix this myself, since the dealer seems incapable and they have no open appointments until after we leave Florida. So, I plan to pull the shrouds and see if an RJ-11 cable is connected and dip switch set to the closed position.  I’m guessing I should have one RJ-11 cable connected at each of my AC units. I’m told I’ll have to do a reset of the thermostat after any change in the dip switch settings. 

Do you think this makes sense?

In all due respect I do not believe that the tech you spoke with at Dometic is correct unless he specifically told you that your old hidden control board is compatible with your new AC units. 

There is no RJ-11 cable that goes to the aquahot on your model year coach.

Off line, please send me info on who you spoke with and their phone number and the model numbers of you new AC units and your old hidden control unit.

[Pduggs]

The tech has yet to fix the bathroom heat. The Aqua-Hot line to the register is cold. Blower at register is working. All other heat registers are functioning as expected including basement heat. The Aqua-Hot electronic controller (pictured) shows zone 1 and 3 are active. 2 is not. 
The tech says I should tap the 2 pump in an effort to get it running. He thinks it might be jammed up, but all the pumps are only a year old and all functioned as expected before the new ACs were installed. 
If the bathroom register works off zone 2 on the AquaHot, how do I get it to operate since zone 2 on the new thermostat doesn’t offer an Aqua-Hot option?  Are the zones listed for the Aqua-Hot different from the zones on the thermostat?

 

[Tom Cherry]

48 minutes ago, Pduggs said:

The tech has yet to fix the bathroom heat. The Aqua-Hot line to the register is cold. Blower at register is working. All other heat registers are functioning as expected including basement heat. The Aqua-Hot electronic controller (pictured) shows zone 1 and 3 are active. 2 is not. 
The tech says I should tap the 2 pump in an effort to get it running. He thinks it might be jammed up, but all the pumps are only a year old and all functioned as expected before the new ACs were installed. 
If the bathroom register works off zone 2 on the AquaHot, how do I get it to operate since zone 2 on the new thermostat doesn’t offer an Aqua-Hot option?  Are the zones listed for the Aqua-Hot different from the zones on the thermostat?

 

YES…they WILL be different. .you need to look at your prints.  The AquaHot Zones in no way, rhyme or reason match the Zones on your thermostat.  The Heat or AH print is quite explicit and you can trace the HVAC zones directly to AH control panel. Just follow the thermostat line from each HVAC zone. 

Once you have that solved, the the next trick is to take the leads (thermostat wires) from a zone that is working….you can control it and you get heat.  Then pull the leads from the zone that does not work (Zone 2…I think…but verify).  Then use the thermostat that is working to bring one the errant zone,  IF a that works, you have an issue with the thermostat or more correctly, the HVAC controller that is supplying the signal or is supposed to,  if it does NOT work….then the issue is in the AquaHot system.

That is the easiest way to test and isolate WHY. 

What I’m not sure of or did not understand…If you have control or can turn on the errant HVAC Zone and the blower in the zone works, then you DO have have an AquaHot issue,  all the HVAC controller is doing is closing a set of contacts.  In reality, you could use a bent paper clip on each pair of the AquaHot “Thermostat” terminals.  What that does is then turn ON the appropriate pump.  The pump contacts are internal and controlled by the main control board.  There is a set of “Blower”or fan terminals.  These terminals go to the fan register(s) for that zone.  The board has a set of pump wires or terminals to control the right pump.

That, in a nutshell, is how it works….

Regardless, as Frank said, you MUST have the right control board for the fourth zone.  Your old zone ain’t gonna work.  You really need to find the print and study this and understand it.

 

 

[Frank McElroy]

2 hours ago, Pduggs said:

The tech has yet to fix the bathroom heat. The Aqua-Hot line to the register is cold. Blower at register is working. All other heat registers are functioning as expected including basement heat. The Aqua-Hot electronic controller (pictured) shows zone 1 and 3 are active. 2 is not. 
The tech says I should tap the 2 pump in an effort to get it running. He thinks it might be jammed up, but all the pumps are only a year old and all functioned as expected before the new ACs were installed. 
If the bathroom register works off zone 2 on the AquaHot, how do I get it to operate since zone 2 on the new thermostat doesn’t offer an Aqua-Hot option?  Are the zones listed for the Aqua-Hot different from the zones on the thermostat?

 

Did you replace the "hidden" zone 4 control board with the new version compatible with your new AC units?  This control board will turn on the zone 2 Aquahot pump if configured correctly