1999 Executive Help Locating 3rd Hidden Dometic A/C Controller Board

[Dean Bennett]

First post - Please to pardon any faux pas. I just acquired the rig and it as an old 4-button system. I have a number of 5-button controllers and 3311557 boards laying around and I was thinking of upgrading to 5-button as I did on my 2000 Windsor. The Executive has 2 Dometic 630215 roof-top units but, three zones show on the 4-button controller. The rig has 3 AH heading zones and 2 AC zones. Despite a call into Dometic and them not knowing if I needed two or three controller boards, my reading of web-posts suggests - If there are 3 zones showing on the controller, there are three controller boards. And, from a wiring perspective, that only makes sense. The two controllers in the AC units are easy to find but, I'm not having any luck locating the third one? I've checked most of the easy places. Anyone got any enlightened ideas where Mondco might have stashed third one on a 99 Exec? Thanks....

[Tom Cherry]

33 minutes ago, Dean Bennett said:

First post - Please to pardon any faux pas. I just acquired the rig and it as an old 4-button system. I have a number of 5-button controllers and 3311557 boards laying around and I was thinking of upgrading to 5-button as I did on my 2000 Windsor. The Executive has 2 Dometic 630215 roof-top units but, three zones show on the 4-button controller. The rig has 3 AH heading zones and 2 AC zones. Despite a call into Dometic and them not knowing if I needed two or three controller boards, my reading of web-posts suggests - If there are 3 zones showing on the controller, there are three controller boards. And, from a wiring perspective, that only makes sense. The two controllers in the AC units are easy to find but, I'm not having any luck locating the third one? I've checked most of the easy places. Anyone got any enlightened ideas where Mondco might have stashed third one on a 99 Exec? Thanks....

Fascinating.....and my comments are generic.  First....I'd start to figure out the system.  If you have ONE thermostat....then there has to be a second Temp sensor in the bedroom.  Then for the 5 button to work, as I am sure you know....you need a Data or Communications (phone line) between the controllers (or the AC's).  SO, this would be my take. 

• Which zones are labeled which.  Zone 1 is probably the front.  Zone 2....now is it the rear (for AC) ... the AH Furnace or Heat zones will be the same) 
• You don't say "What KW or size they are".  The 15 KW (at least in the early 2000's) had the controller in the Roof Top unit.  There are TWO phone or Data (male) terminals that hang down.  They are in the Plenum and you can see them easily with the filter or the cover off.  
• Zone's do NOT have to be cabled in the order they are numbered.  That is because the Thermostat sends out a coded MPX signal.  You have a data pair and a low, very low....5 VDC? power for the Thermostat.  OK....also, the 13.5 KW had the Controller INSIDE in the plenum.  
• SO....here is what I think.  IF you look up front...there should be TWO inline phone (communication cable) connectors.  They are, INDEED, phone connectors as they just hook up the same colors.  SO....two connectors UP FRONT....one from the Thermostat and the other from the OUTGOING line to the rear (or hidden) unit.
• In the back.  If there is only ONE connector there and there is a hanging (or coming from the controller) an UNTERMINAED male phone plug....then you "assume/know" that the controller is somewhere in the middle.  Hidden behind a panel in a cabinet or whatever.  NO WAY, unless someone else found theirs, to see.  
• Each Controller should have a DIP switch panel.  TYPICALLY the first 3 were ZONES.  SO, Zone ONE (1) was by default....if the other three switches (Z 2, Z3, or Z4) were NOT turned on or closed.  The Furnace on all three HAS to be on to trigger the AH system. The fact that the hidden controller does NOT have an AC hooked up to it tells it that it is a standalone and is only there for heating.
• That Zone, TYPICALLY, will have a remote sensor in the middle...or wherever the hidden zone is.  BUT...again....this is Monaco and they were learning and making mistakes....sometimes they forgot to hook up the REMOTE.  IN THEORY....your Bedroom should have a REMOTE.  That is what controls or tells the thermostat what temperature it is.  Doesn't matter in Heat or Cool.  So, the rear unit will have a thermostat lead and you should have a remote on the wall.  NOW....they did goof on one unit and the upfront (middle) Thermostat was actually the sensor for the bedroom.  ONLY Monaco.
• The Hidden (zone 3....most likely) controller should (must?) have a Temp or remote sensor.  SO....find that sensor for the THIRD AH zone....and then start looking behind panels or such (inside cabinets where you pull out a panel)....
• NOW....the real question.  WILL the older AC's work on the controller's you have.  You will need to have the communication cables or dangling terminals.  You will need AC power.... You will NEED DC power (although if ONLY one of the controllers has DC....in theory, they all will work).  Sometimes the hidden one will NOT have a DC input. Then they will have a REMOTE sensor (assuming they need it). Finally, there will be a pair of wires that connect to the AH.  These wires are just a switch leg.  There is NO 12 VDC coming out of the two "Furnace" controller leads or terminals.  When heat is needed....the contracts close....and then the internal 12 VDC on the AH control panel go to work.

That's as much Dometic 201 as I know...

[Dean Bennett]

Tom,

Thank for the response!

• Zone-1 (front) uses the internal thermostat. Has AC, Heat and Furnace options.
• Zone-2 (Middle) uses an external Dometic thermostat. Has Furnace option (AH).
• Zone-3 (Back Bedroom) uses an external Dometic thermostat. Has AC, Heat and Furnace options
• The 630 Series Dometic units are 13.5K “BTU” rated that have the controllers in them
• Per Dometic and the 4-Button to 5-Button conversion kit, the boards I have work on 630 Series units.

So – The middle unit has the ‘hidden’ controller. It has a thermostat in the hall whose wire ‘appears’ to go straight down. The board is not obvious in the cabinets that surround the path going down. It is not around the AH unit in the bay below but, there are bay ceiling covers in the bays that the thermostat wire may come down into. I was hoping someone with a 99 Exec or, experience working on one might have a tip-off before I start disassembling the rig. I’m just finishing up changing the 8 air bags and one HWH slide cylinder so, I’m growing weary of ‘digging’ around 🙂 

Thanks!!!… Dean
 

Edited May 22, 2023 by Dean Bennett

[Bruce S]

As I recall, this module in our 98 Signature was located in the hidden compartment above the refrigerator.  On our coach, the tank monitoring display, etc. was located on the front of this compartment.  Since the coaches are close in vintage yours may be in the same place.  They had to put it somewhere didn't they... 🙂