No power to themrostat

[nvrtoofast]

On shore power in my 2006 Camelot. AC was running fine. Sometime in the night the Thermostat lost power. I have a MicroAir Touch. I happen to have the old dometic thermostat in a cabinet. I swapped it and no power to it either. Where does Power for the cable come from. I've cycled the breakers just in case and nothing. Any help is appreciated. Going to be a hot day.

 

[nvrtoofast]

UPDATE: Located the board in the front AC unit. Checked the fuse and it was good. Unplugged and reattached. No change in power to Thermostat.

 

[jacwjames]

I have a 15 amp fuse in my bedroom 12 volt distribution panel for the AC's

On mine the communication wire is daisy chained so check all connections.

 

[Guest Ray Davis]

Up inside my ACs, I have what looks like phone wires & connectors, those little plug-together connectors are bad about losing their contact.  Usually just unplugging & replugging a few times is enough to reestablish contact. 

[nvrtoofast]

Thanks.

- Panel fuse: Good
- Unit fuses: Good
- Phone wire connectors: all "cycled" and should be as good as can be expected. Front rear and thermostat.

- Main breakers: cycled Unit breakers for 30 seconds then Main breaker for another 30.

- Control boards: Opened up front and rear. Both "look" Kosher

Not sure what I'm missing

 

[jacwjames]

How many AC's do you have?  Do you know the routing of the communication cable??

Go to the AC which has the 12 volt power supply connected, in my case it is the front but yours could be different.  Try plugging the thermostat into there, unplug the communication wire and plug in the thermostat there.  That would bypass the rest of the system. 

If you don't have power to the thermostat then I'd check the 12 volt wire connector.  In my case it was a blue wire, yours may different.  You should see 12 volt on that wire.  

[nvrtoofast]

Thanks for the thought. I swapped plugs on the front unit and plugged in the T-stat on the cable to the rear unit. No Joy. Did the same to connect to the rear unit. No Joy. Reached out to Micro-air (t-stat) and they contacted immediately. They advise to unplug for 1 hour and then call back. I will have a call with them in about 30 minutes. The contact is knowledgeable and is clearly looking to know the issue to better the product. Good company.

[Ivan K]

My thermostats 12V power originates from 2A fuse in bedroom cabinet.

[nvrtoofast]

Thermostat still will not start. Micro-air is sending a new one out. Not 100% sure that is the fix but have no idea honestly.

Pulling out the multi meter.

 

Pulled the board. Looked good on the back. Any Ideas where to look next?

194FEC3B-CBAA-40EA-88C5-50E1CFD28E79.heic

[Tom Cherry]

Started writing this…..and agree….but….will comment and then explain or answer your questions….

You say, I think, NO POWER to Control Mod….that means the upfront unit and on a 15KW, on the roof….on a 13.5 inside in plenum.  You probably know this….and many do, but many do NOT.  So read along.  Unless this is clear, random VOM is just a crap shoot.

YES, you have to use the control boards or modules in the AC’s….  I am making an assumption here…you STILL have your original Penquin or Domeric AC and just replaced the thermostat.  You can pull the wiring, but l’m 99.99%, this is what you have.

The salesman’s solenoid brings in power to the “house fuse box”.  Now, on the later Camelots, there was a bank of Circuit breakers hidden behind a panel near the House fuse panel.  We have prints on the 2006.  The electrical wiring for the Windsor (last year), Camelot and Scepter were identical.  We have those prints.  

there is a print for HVAC.  There is also a print for House Fuse panel.  The routing is this….main power comes from a buss or a connection.  You may  have one circuit breaker between the source (salesman solenoid).  That may be in the 50A or so range.  It may be in the RRB or inside near the House 12 Fuse panel.  IF…and please CHECK this, you have 

Assuming you have power on ALL the fuses on the 12 VDC fuse panel, then there is a BREAK or a bad connection in the downstream circuit….

THERE ARE NO MORE FUSES.  Each control module has incoming 12 VDC power.  In reality, that was a Monaco “OVERKILL”.  If you have 2 AC, then power to EITHER Module will run the system.  That is clearly stated in the installation manual and the set up of the old Dometic thermostat.  BUT if you lose the “data connection” as in the 2 pair or the “phone cable”, then on the old system….you had to find the open or faulty connection.  Fix it and reset it.  Just plugging in the old should NOT have worked unless the did the Switch OFF, MODE & ZONE control buttons held in and switch ON.  FF means all is reset.

NOW….to do that, 2 of the data cable are DC Volts (5? Or so??.).  The other two are the Multiplex 2 wire circuit which takes the signals from the modules and translates them into “on and off and auto or whatever).  SO….reality, and I have talked to Microaire and they told me this….

WE DO NOT KNOW HOW TO TROUBLESHOOT THE SYSTEM.  That is YOUR responsibility.  We just reverse engineered their thermostat and made one that will be a clone…but have the features you want.

NOW….if you are SURE that the OLD thermostat was GOOD….and it did not light up.  The replacement Microaire will not work.  There is, most likely a data cable issue .  WHERE….god only knows.  So here goes….

The first thing to do is take the OLD thermostat.  You have 2 connected phone cables up front and one in the rear.  Those plugs are NOT specific.  If you remove BOTH as in disconnecting BOTH phone inline connectors (mark which data cable was connected to each), THEN pug in the OLD thermostat to one of the two dangling or coming out of the top (assuming a 15K)…you should see the Thermostat display light.  Again….you can also try the Microaire.  NO DISPLAY….no POWER coming from that control module,  so the same on the back.  No display, no 12 VDC on the module.  The old one or the new one has to have voltage from the MODULE via 2 of the data cable or “a pair”.  

IF you have incoming 12 VDC to the Module…..you can google the install manual….make sure you say OLD PENGUIN DOMETIC INSTALL…there is a print and color for that power.  Again….the house fuse feeds the rear one…and there is a tap or T in that line and the wire goes up front,  NADA goes to the Thermostat.  Look at the prints,

I don’t know where to tell you to start…but find the incoming DC to each control module.  Good DC….then next….either thermostat, plugged in DIRECTLY will power or light up the display….100% if the Module is OK.

NOW!!!!!  Did you plug and UNPLUG the dangling connectors at the MODULE.  THEY can be corroded.  Clean every male and female connector (cooper tabs) with Alcohol on a Qtip and seat and reseat several times.

CONCLUSIONS….a NEW Microaire ain’t gonna work, if your OLD thermostat display was OK and good connection.  The power for the Microaire comes through the data cable.  You have got to have voltage to either, so that automatically raises the red flag.  If you have voltage incoming to the control modules and they are working or if only ONE is working….display on.  The issue is IN YOUR DOWNSTREAM side.  Good that you are getting a new one…so, IF the old Tstat didn’t have a good connection or the display is gone….that is the issue.  BUT you have also got to have votlage (maybe 12, but milliamps) at the thermostat end…on two wires….otherwise…no joy.

Sorry for the length and not talking down to you….to troubleshoot….you have to  how it works and that the fact there is redundancy in that power to EITHER module will run the system….Good Luck…keep us posted….

 

 

 

 

[nvrtoofast]

Thanks Tom. I've been running down most of these areas. All other 12V items are on. So panel is good and it is pushing 12+V. I'll check behind the panel for any other circuit breakers. Hopefully, I find one and can stop.
 

I've played with the phone cables and nothing worked. Will try to check for 12V power at the boards. Both units were running till they all stopped and display went dark. It all doesn't go wrong at once. So I am surely looking for a specific item.

[nvrtoofast]

I've developed a plan. After examining the schematics and what is in the roof. I DO NOT have 12V_DC to the front controller. It appears the rear controller did everything. It has the White and Red wire that are confirmed 12V with my Multi-meter. So the rear controller board may be dead.

 

I will swap the front and rear controller to be sure. While disconnected, I will pull the rear board from the casing and inspect.

Fingers crossed that I may have found it.

[nvrtoofast]

Good news: Moved the front control board to the rear, where I have power for the board. I got the thermostat to light up.

Bad News: I need a new board to replace the bad one that was in the rear.

I'll update when I have a new board.

 

On a side note. I'm perplexed why there is no power wire to the front unit. Original unit, so I figure it should be there.

 

[Tom Cherry]

3 hours ago, nvrtoofast said:

Good news: Moved the front control board to the rear, where I have power for the board. I got the thermostat to light up.

Bad News: I need a new board to replace the bad one that was in the rear.

I'll update when I have a new board.

 

On a side note. I'm perplexed why there is no power wire to the front unit. Original unit, so I figure it should be there.

 

Hey, every once and awhile, I find a nut.  The Control Boards are usually pretty robust.  We have a "pecking order" that most of us use....based on what folks have found.  90% are connections....without fail...and cleaning them works.  I think I have 25 notches in my "pistol grip" for that.  Then Thermostats are next......but sometimes Control Modules.  This is for units where you "loose" a display or can't find a zone.

NOW...for your reading pleasure... I find this.  I do a LOT of posting from my iPad.  So, tonight I was on the PC where all my "goodies" live.  Another person is having a "Won't start up" on Auto and the fan motor is the issue (we think).  I found this for him and then thought about you.

Good Luck.  NOW...as to the WIRING.  EVERY ONCE AND A WHILE...Monaco GOOFS.  Do you HAVE the 12 VDC power wire to the "bad module" or did they just forget to run it.  As I said, the system is designed for such low (milliamp) current that even ONE good unit will provide power.  

NOW, I am a bit confused and it has been a LONG day....trying to figure out why the wife's 2014 ATS no longer has AC.  If you thing the MH are tough, you can barely find the AC Compressor and there are all sorts of sensors and such.  POWER and the Control Relay work...but the engine is running cool however, the main tank is low....VERY low.  Bottom line....I GIVE UP.  Time to say... FIX IT....

ANYWAY...my brain is tired.  I MAY have figured it out.  SO, if you did this or tried this, it would have worked.  The control unit is nothing more than a "whistle stop" like a remote dumb terminal.  The front board has an issue.  The circuit to PASS THROUGH the Voltage from the rear is bad.  However, if there was DC up front, would it have worked....?  Maybe NOT worth the chase.  It would be interesting, for me...maybe others...if you ran a temp line to the front board.  If it THEN worked, then we know that if you DO have 12 VDC and there is a problem on the board, then it WILL take it's power and supplement or provide power.  Just curious.

BUT, I still stand by my statement.  A NEW Microaire would not have solved the issue...you GOTTA have 12 VDC at each location.  You can read this for info...it goes into more detail that I thought.  Good RESOURCE.  Keep us posted on the final solution...

 

ccc5 Trouble Shooting.pdf

[nvrtoofast]

On 7/28/2023 at 7:56 PM, Tom Cherry said:

ANYWAY...my brain is tired.  I MAY have figured it out.  SO, if you did this or tried this, it would have worked.  The control unit is nothing more than a "whistle stop" like a remote dumb terminal.  The front board has an issue.  The circuit to PASS THROUGH the Voltage from the rear is bad.  However, if there was DC up front, would it have worked....?  Maybe NOT worth the chase.  It would be interesting, for me...maybe others...if you ran a temp line to the front board.  If it THEN worked, then we know that if you DO have 12 VDC and there is a problem on the board, then it WILL take it's power and supplement or provide power.  Just curious.

ccc5 Trouble Shooting.pdf 672.56 kB · 6 downloads

This IS interesting AND I wish I had tried it. I could have easily run a temp power to that unit. It would have also centered the issue to the rear unit/board. I'll need to put a roll of wire in my travel kit. Good idea!

AND 100% the new unit would not have fixed it. I doubted it was the issue myself.

I'm somewhat confused why they even use a 12V source when the units can't run without 120v. I'm not an electrical engineer. I'll leave that conundrum to them.

I'll see if I can clean the corroded pots as they definitely looked bad and the board looked good. I just didn't have any vinegar handy.

[jacwjames]

My guess it's just like a home HVAC system, which used 24 volt for the thermostat control. 

We have a split system at home for the basement and first floor, each thermostat communicates to a central control board that controls the HVAC unit and the automatic dampers that direct conditioned air to the two floors.   Both thermostats are located to provide the best control for the separate floors, first floor central in family room and basement located in the furthest bedroom, this is done to hopefully balance the condition air where needed, very similar to an RV. 

[Tom Cherry]

15 hours ago, nvrtoofast said:

This IS interesting AND I wish I had tried it. I could have easily run a temp power to that unit. It would have also centered the issue to the rear unit/board. I'll need to put a roll of wire in my travel kit. Good idea!

AND 100% the new unit would not have fixed it. I doubted it was the issue myself.

I'm somewhat confused why they even use a 12V source when the units can't run without 120v. I'm not an electrical engineer. I'll leave that conundrum to them.

I'll see if I can clean the corroded pots as they definitely looked bad and the board looked good. I just didn't have any vinegar handy.

Simple Monaco was lazy and STUPID…and the Intellitec EMS was never designed to work or shed proper when using the Dometic MPX thermostat technology.

WHY….  First, the Intellitec EMS was ALSO never designed to load shed a 20A INDUCTIVE load.  The relays were rated for “plain” Non Inductive load.  A bank of lights or a heater (without a fan motor) or toaster or water heater is a RESISITIVE Load.  A Motor has to have a spike in voltage to start.  Not getting deep into every motor, but our HVAC units are inductive and they have a starting capacitor that zaps a higher voltage and amperage when the start.  That is why younwill see up,to 17 amp breifly.  Put on an oscillliscope or a precise voltage and current recording (digital) where you can see the voltage and amperage in nano or microsecond intervals….it goes uo.  BRIEFLY, but it eventually chews up the contacts on the FOUR 120 VAC shedding relays.  Presumably for a water heater.  BUT…there are THREE additional relays for shedding HVAC.  They are supposed to turn ON and OFF a conventional thermostat that send out a 12 VDC signal.  Some earlier Monacos had such.  BUT when Monaco went to the 4,5 or 10/12 Thermostat….there is NO 12 VDC signal to interrupt.  The ONLY way to KILL a Dometic would have been to have added an AUXILIARY 12 VDC relay, next to the control module, which would have switched the 120 VAC.  Every home HVAC unit with an Outdoor Compressor has a 24 VAC relay that closes and makes the 220 VAC circuit.  When the Thermostat says OFF….that relay opens.  Those and the starting capacitors are what every HVAC tech has in his truck and the two most common “failures” other than “we ain’t got no freon”.

OK….now this is where it gets tricky.  The Dometic HVAC MPX system will RUN even if only ONE control module has 12VDC, since the communication cable powere the entire system….and is where the THERMOSTAT gets power.  Thus, you can’t shut down a front AC….IF MONACO HAD run a Switched or SHEDDING 12 VDC.  The rear would have run it.  NOW…stay with me.  IF you had a thermostat for every unit….and some 2 HVAC MH’s had…YES, you could have run the 12 VDC from the EMS shedding AC relay to the front and the same for the back.  THEN, killing the 12 VDC to a specific unit control module….NOT MULTIPLEXED with other units…that was possible.  BUT the selling point of the Dometic MPX system was THAT.  Only data cables to run.  Only ONE source of 12 VDC needed to only ONE control module.

Pity the MH manufacturers and Intellitec and HVAC manufacturers never would talk or just “threw up their hands”.  We see it here.  We see the EMS board failures.  We actually understand the systems better than some RV TECHS….GOD SAVE US ALL.

if that is fuzzy…call me…I’ll try to explain.  I have been requested from time to time to do a PAPER on how the MPX and EMS and Load Shedding and failures occur.  I can NOT take credit for being the first to concoct this scenario.  I had a good teacher and a EE background from 2 years before I changed my Engineering major and over 30 years of maintenance….and, dumb me…self taught himself basic house wiring at age 13….so, in reality…I’ve been a “electrical circuit nut” for 65 years.  IT finally, started to make sense and, after a lot of noodling and reading and circuits research , it all came together and thus, assist in problem solving.

4 hours ago, jacwjames said:

My guess it's just like a home HVAC system, which used 24 volt for the thermostat control. 

We have a split system at home for the basement and first floor, each thermostat communicates to a central control board that controls the HVAC unit and the automatic dampers that direct conditioned air to the two floors.   Both thermostats are located to provide the best control for the separate floors, first floor central in family room and basement located in the furthest bedroom, this is done to hopefully balance the condition air where needed, very similar to an RV. 

Yes….snd maybe NO….read my epistle….LOL…you are smarter than me and will instantly understand….and that is a serious comment…

[jacwjames]

34 minutes ago, Tom Cherry said:

…you are smarter than me and will instantly understand….and that is a serious comment…

I am sure I am not smarter then you but I am stubborn enough to keep looking at a problem until I understand it enough to fix it. 

 

 

 

[Tom Cherry]

19 minutes ago, jacwjames said:

I am sure I am not smarter then you but I am stubborn enough to keep looking at a problem until I understand it enough to fix it. 

 

 

 

Au Contre….admittedly we both had unique careers…..and we both had hands on experience.  My little jab was to kid you that NO, our Dometic MPX systems do not work like anything that one has in a home, unless one has “a smart @$$ system”….where you can control multiple AC or heating systems….but you do NEED to remove, sometimes, or modify the existing (usually buy a SMART Tstat from Amazon).  THEN EVERY unit is physically wired or networked together.  BUT with a voice operated device…HEY ALEXA OR SIRI…with a “smart phone”.  But one has also MIGHT spend MORE on energy as the Alexa units may (probably) don’t have all the energy saving technologies that are proprietary to Honeywell or Johnson Controls.  install an interface module or different, SMART  thermostat on each and they will be “BT’ed” together so you see each screen and program or  control. It.  BUT…Honeywell is closing the gap and making their really sophisticated thermostats that will network…. They have the best (IMHO) energy efficiency and multiple use thermostats out there.  Mine does everything except wake me up. It “recovers” from HP or AC and then does a controlled startup…so, it i set the NIGHT period to 80 degrees for AC and want the WAKE UP period to be 75….it “learns” when to come on…and the outside thermostat also tells it what is going on.  Same for HP….a REAL savings.  A HP thermostat withiut s RECOVERY function will slam onnthe aux strips at 7:30 (set point) and soak upmthe KWH.  But a recovery Tstat will start the HP compressor maybe 3:00 and use way less jucie than the strips.

Bottom line…the post was to educate and explain and also lay out WHY the EMS and the Intellitec MPX were NOT compatible….and Stupid Monaco wired them for self emulation….or suicide….

NOW…folks with Coleman floor systems…a AC/HP with gas burner is totally different.  Add in a front Coleman AC with a DIRECT 12 VDC signal(s)…YEP…the EMS would work….  Winnebago did this on my Adventurer….