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Front Air Conditioning Unit Randomly Shuts off Leaving Thermostat Blank for Zone 2


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The Zone 2 (front) air conditioning in our 2002 Windsor will randomly shut down (without reaching the set temperature) after running for anywhere from 20 minutes to 3.5 hours. Zone 1 has will still have all functions available. Zone 2 in the thermostat, is blank and there are no functions available. I can get it to work again by turning off the master switch at the bottom of the thermostat for a while, then back on. All functions return to zone 2 for a while. Years ago, in the winter, the propane heat for Zone 2 failed and I tracked it down to a bad AC control board in the front unit.  At that time, I also replaced the 5 button thermostat with a spare that had come with the motorhome. It's too hot out now to swap out the control boards between the two air conditioning units to test, so I've just ordered a new control board, and a Micro-Air thermostat to replace the old 5 button one in case it's a thermostat problem.

When this first happened, we were in a state park with a 30 amp hookup, and I thought maybe as it was a low voltage situation and the EMS kicking in, as I've had that happen before in a state park when the voltage dropped to 90VAC. This time, it also happened twice while running the generator to power zone 2 air conditioning while driving. 

I have two questions.

1. Since the associated propane furnace won't function with a bad AC power control board in the heat pump unit on the roof, will a bad board in the furnace impact air conditioning operation?

2. Should I be checking something else?

Thanks in advance!

AlanC2

02 Windsor PST

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10 minutes ago, AlanC2 said:

 

When this first happened, we were in a state park with a 30 amp hookup, and I thought maybe as it was a low voltage situation and the EMS kicking in, as I've had that happen before in a state park when the voltage dropped to 90VAC.  

Yikes 😳!

Most EMS surge protectors will kill power at about 104V.

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You really need to clean all the RJ11 telephone data cord connections.  Start by cleaning the connection in the back of your thermostat.  Then drop the inside covers under each A/C unit.  Some of the A/Cs will have an RJ11 junction connector.  Make sure you clean (and maybe replace) the connections on it as this is most likely your problem spot.  

I like to use Hosa DeOxit electrical cleaner available on Amazon.  It not only cleans the connectors but also deoxidizes and protects the contacts.  

https://www.amazon.com/Hosa-D5S-6-DeoxIT-Contact-Cleaner/dp/B00006LVEU?th=1

Once you have cleaned ALL connections, perform a thermostat reset.  Slide the black on/off switch underneath the thermostat to off.  While holding down the top and bottom buttons, slide the black switch on.  Wait until you see FF in the display and then release the buttons.  Hopefully all of your heating and cooling modes will return.   

Also, I would do this before installing the new thermostat and control board.  This will make sure you have a good system before modifying it.  

Edited by vito.a
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16 minutes ago, vito.a said:

You really need to clean all the RJ11 telephone data cord connections.  Start by cleaning the connection in the back of your thermostat.  Then drop the inside covers under each A/C unit.  Some of the A/Cs will have an RJ11 junction connector.  Make sure you clean (and maybe replace) the connections on it as this is most likely your problem spot.  

I like to use Hosa DeOxit electrical cleaner available on Amazon.  It not only cleans the connectors but also deoxidizes and protects the contacts.  

https://www.amazon.com/Hosa-D5S-6-DeoxIT-Contact-Cleaner/dp/B00006LVEU?th=1

Once you have cleaned ALL connections, perform a thermostat reset.  Slide the black on/off switch underneath the thermostat to off.  While holding down the top and bottom buttons, slide the black switch on.  Wait until you see FF in the display and then release the buttons.  Hopefully all of your heating and cooling modes will return.   

Also, I would do this before installing the new thermostat and control board.  This will make sure you have a good system before modifying it.  

Thanks for responding, I'm familiar with DeoxIt I forgot to mention that I did hit the RJ11 connections on the back of the thermostat, and on the heat pump unit (accessible from inside) with electrical contact cleaner, working them a few times and also did the hard reset on the thermostat. I did not go up on the roof to access and clean the RJ11 connection on the control board though. The air conditioning shut down after 20 minutes on generator power. It's just too hot here in Maryland to spend a lot of time on the roof, so I will clean the contacts up there when I replace the control board.

AlanC2

02 Windsor PST 

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Some like BEER.  Some like WINE.  I do NOT recommend using Detox for a contact cleaner.  Plain old Isopropyl Alcohol is safer and works better.  Q-Tips are your friend. Vito is RIGHT.... you have a CONNECTION PROBLEM.  SO....lets address that and also answer your questions before you start throwing parts at a problem that isn't there.

CLEAN THE RJ Connectors....ALCOHOL or PLAIN CRC ELECTRONIC CLEANER.  This is SAFER.  NOW, if one has used DeTox...and it works....then that is fine.  BUT due to the age of these connectors and the brittleness of the plastic and the chemical composition of the plastic, my experience is to use a MILD solvent cleaner and CRC and Alcohol will cause less damaage.

I also carry SPARE connectors.  Typically, the FRONT AC is Zone 1.  IF it reads Zone 2 and it USED to work...then let's not quibble or speculate.  Maybe SOMEONE replaced the controller or decided they wanted it to be #2.  There is a set of DIP switches on the controller.  If NONE of the ZONES are ON or set...the default is Zone 1.  SO, where ever your Thermostat is (main galley or hallway), it is "backwards" to how Monaco USUALLY and MAYBE the Windsors were DONE that way.

MOVING ALONG.  There may be ONE or TWO inline (called Dual Inline Connectors) in the Plenum. There are TWO RJ wires hanging down.  There is at least ONE other RJ or maybe 2... Have NO IDEA.  You just need to put a piece of tape on the ONES hanging down from the ceiling.  They are NOT polarized....they work with EITHER of the other TWO or ONE if you only have ONE.

Here is how this nightmare works... THERE might be a POP QUIZ.  There is 12 VDC power to EACH AC unit.  That is what runs the Control Board. There is a data cable (the lines LOOK with PHONE lines...they are NOT...they have a different RJ termination color code or sequence...a PHONE cable is the same on each end.  These are reversed.  LIKE 1234 (or the colors) the OTHER end is 4321.  DON'T ask for more.  You can NEVER substitute or use a PHONE cable. You CAN cut off one END of a Phone Cable and reverse the colors and that is NOW a DATA cable.  It won't work on a PHONE....

OK...The PROPER WAY TO START.  Pull off the Filter covers.  Then locate the two dangling or hanging down RJ's. These are FROM THE CONTROL UNIT. ON the 13.5's they were (maybe) in the plenum.  On the 15's they are only accessible from the root after you PULL the cover.  They then have the connectors and go to other DATA CABLES.. 

This is HOW Monaco USED to run them.  Thermostat has a data cable.  IT runs (TYPICALLY) to the FRONT AC.  Then that Thermostat cable is connected to ONE of the hanging ones...the other Hanging ONE then goes to another Data Cable.  THAT data Cable goes to the REAR AC.  There is NOT another data cable there.  This is the END of the line.  SO, there will ONLY be ONE connector (Dual Inline).  PULL OFF one Dual INLINE at a TIME.  Clean the MALE connectors and the FEMALE internal CONTACTS.  THEN reconnect.  Plug and unplug about 3 times.. FIRMLY push in each time.  This cleans the contacts.  REPEAT for ALL the Dual INLINE connectors.

NOW, you have NOT been doing the PROPER RESET.  This is the way it MUST BE DONE.  TURN OFF the switch on the bottom of the Thermostat.  WAIT about 3 minutes.  THEN hold ON or PUSH IN the MODE and ZONE buttons....WHILE THEY ARE HELD IN...THEN turn on the POWER.  There will be an FF in the Display.  BINGO....you have successfully RESET the System. The thermostat has NOW "TALKED to " or done the HANDSHAKE with the two controller.

There is NO 12 VDC line to the Thermostat.  There is 12 VDC on TWO of the wires or one "PAIR". 

NOW....you should have EVERYTHING working.  If you lose or can't find a ZONE...or a function as you CYCLE or toggle through the Thermostat.  GO BACK AND CLEAN AGAIN.  I have replaced my Dual Inline connectors and ALWAYS HAVE SPARES.  You have GOT to have a ROBUST or solid connection between the FOUR contact.

NEXT UP.. word to the wise.  NEVER, again, use the BOTTOM SWITCH.  ONLY USE IT TO RESET. TO TURN OFF a ZONE...select the ZONE  THEN Toggle through wih the MODE button....to OFF.  The switch is mechanical and often fails.  SO DON"T abuse it..

NOW...without MORE feedback...IF you have NEVER done the RESET...then you have been LUCKY.  You HAVE TO RESET the system (From the Thermostat) every time you break or disconnect one the DATA CABLE connections.  They get moisture and dust and vibrate all the TIME.  The tiny surface areas get corroded.  Replacing the Dual Inline (Amazon has them) is the best way to get it fixed...

NOW... the BOARD or the MODULE is erronously named AC CONTROL.  YES...it controls the POWER to the Compressor as well as reversing the Valve for HEAT and Cooling.   BUT it also has another purpose.  Your FURNACE has to have a SIGNAL.  Many folks think, and are incorrect, that the Control Board sends "POWER down to the Furnace.  WRONG>  The two wires (commonly called BLUE) GET NO VOLTAGE or SIGNAL or any "electricity" from the Control Board (Module).  There is a RELALY.  When the Thermostat, in the HEAT or FURNACE mode, needs HEAT....it signals the Control BOARD. The Furnace or HEAT relay closes. The FURNACE has TWO wires.  When the TWO WIRES in the Control Box are JOINTED (Think of the relay as a LIGHT SWITCH), you TURN ON THE SWITCH.  When those two wires make a circuit....then the FURNACE starts.  There is NO 12 VDC signal.  Just the Control Board closing a contact and then the Furnace TAKES over. 

That's it.  Do you have a BAD module? Who KNOWS?? DO the above.  THEN test.  ODDS ARE (more than 90% of the issues and that is well over 100 members or folks saying...I LOST A ZONE...are in the RJ connections.  I had to clean mine THREE times...and I "know how" one time.  That is when I ordered NEW connectors...but that was 4 years ago and all is well.  GO FIGURE.  Thus, we have less than 10 BAD BOARDS or CONTROL Modules.  YES, they BREAK.  BUT, the issue is in the connection...and if there is the tiniest gap...and it vibrates...the Thermostat "forgets" who's their buddies.

In addition, if one never does the RESET...then that will make this happen.  Dometic says...RESET every time an RJ cable is disconnected.  RESETTING is the FIRST STEP after install.  The Thermostat has NO IDEA how many controllers are out there and how they are configured (some with HEAT and some without) and the NAME (zone 1 or 2 or 3.

Good Luck.  Let us know.  I would NOT REPLACE anything until you properly clean and reset, per the Dometic Protocol.

Let us know.

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Replace the inline couplers as a possible source of issues as well. After cleaning mine a few times and chasing ghosts I just replaced them and tore the old ones apart for inspection. I found corrosion and some questionable connections inside. They live in the updraft area and where I live there is tons of moisture in the air. And at 15 yrs old, they have vibrated constantly and outlived two air conditioners. 

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18 hours ago, Tom Cherry said:

Some like BEER.  Some like WINE.  I do NOT recommend using Detox for a contact cleaner.  Plain old Isopropyl Alcohol is safer and works better.  Q-Tips are your friend. Vito is RIGHT.... you have a CONNECTION PROBLEM.  SO....lets address that and also answer your questions before you start throwing parts at a problem that isn't there.

CLEAN THE RJ Connectors....ALCOHOL or PLAIN CRC ELECTRONIC CLEANER.  This is SAFER.  NOW, if one has used DeTox...and it works....then that is fine.  BUT due to the age of these connectors and the brittleness of the plastic and the chemical composition of the plastic, my experience is to use a MILD solvent cleaner and CRC and Alcohol will cause less damaage.

I also carry SPARE connectors.  Typically, the FRONT AC is Zone 1.  IF it reads Zone 2 and it USED to work...then let's not quibble or speculate.  Maybe SOMEONE replaced the controller or decided they wanted it to be #2.  There is a set of DIP switches on the controller.  If NONE of the ZONES are ON or set...the default is Zone 1.  SO, where ever your Thermostat is (main galley or hallway), it is "backwards" to how Monaco USUALLY and MAYBE the Windsors were DONE that way.

MOVING ALONG.  There may be ONE or TWO inline (called Dual Inline Connectors) in the Plenum. There are TWO RJ wires hanging down.  There is at least ONE other RJ or maybe 2... Have NO IDEA.  You just need to put a piece of tape on the ONES hanging down from the ceiling.  They are NOT polarized....they work with EITHER of the other TWO or ONE if you only have ONE.

Here is how this nightmare works... THERE might be a POP QUIZ.  There is 12 VDC power to EACH AC unit.  That is what runs the Control Board. There is a data cable (the lines LOOK with PHONE lines...they are NOT...they have a different RJ termination color code or sequence...a PHONE cable is the same on each end.  These are reversed.  LIKE 1234 (or the colors) the OTHER end is 4321.  DON'T ask for more.  You can NEVER substitute or use a PHONE cable. You CAN cut off one END of a Phone Cable and reverse the colors and that is NOW a DATA cable.  It won't work on a PHONE....

OK...The PROPER WAY TO START.  Pull off the Filter covers.  Then locate the two dangling or hanging down RJ's. These are FROM THE CONTROL UNIT. ON the 13.5's they were (maybe) in the plenum.  On the 15's they are only accessible from the root after you PULL the cover.  They then have the connectors and go to other DATA CABLES.. 

This is HOW Monaco USED to run them.  Thermostat has a data cable.  IT runs (TYPICALLY) to the FRONT AC.  Then that Thermostat cable is connected to ONE of the hanging ones...the other Hanging ONE then goes to another Data Cable.  THAT data Cable goes to the REAR AC.  There is NOT another data cable there.  This is the END of the line.  SO, there will ONLY be ONE connector (Dual Inline).  PULL OFF one Dual INLINE at a TIME.  Clean the MALE connectors and the FEMALE internal CONTACTS.  THEN reconnect.  Plug and unplug about 3 times.. FIRMLY push in each time.  This cleans the contacts.  REPEAT for ALL the Dual INLINE connectors.

NOW, you have NOT been doing the PROPER RESET.  This is the way it MUST BE DONE.  TURN OFF the switch on the bottom of the Thermostat.  WAIT about 3 minutes.  THEN hold ON or PUSH IN the MODE and ZONE buttons....WHILE THEY ARE HELD IN...THEN turn on the POWER.  There will be an FF in the Display.  BINGO....you have successfully RESET the System. The thermostat has NOW "TALKED to " or done the HANDSHAKE with the two controller.

There is NO 12 VDC line to the Thermostat.  There is 12 VDC on TWO of the wires or one "PAIR". 

NOW....you should have EVERYTHING working.  If you lose or can't find a ZONE...or a function as you CYCLE or toggle through the Thermostat.  GO BACK AND CLEAN AGAIN.  I have replaced my Dual Inline connectors and ALWAYS HAVE SPARES.  You have GOT to have a ROBUST or solid connection between the FOUR contact.

NEXT UP.. word to the wise.  NEVER, again, use the BOTTOM SWITCH.  ONLY USE IT TO RESET. TO TURN OFF a ZONE...select the ZONE  THEN Toggle through wih the MODE button....to OFF.  The switch is mechanical and often fails.  SO DON"T abuse it..

NOW...without MORE feedback...IF you have NEVER done the RESET...then you have been LUCKY.  You HAVE TO RESET the system (From the Thermostat) every time you break or disconnect one the DATA CABLE connections.  They get moisture and dust and vibrate all the TIME.  The tiny surface areas get corroded.  Replacing the Dual Inline (Amazon has them) is the best way to get it fixed...

NOW... the BOARD or the MODULE is erronously named AC CONTROL.  YES...it controls the POWER to the Compressor as well as reversing the Valve for HEAT and Cooling.   BUT it also has another purpose.  Your FURNACE has to have a SIGNAL.  Many folks think, and are incorrect, that the Control Board sends "POWER down to the Furnace.  WRONG>  The two wires (commonly called BLUE) GET NO VOLTAGE or SIGNAL or any "electricity" from the Control Board (Module).  There is a RELALY.  When the Thermostat, in the HEAT or FURNACE mode, needs HEAT....it signals the Control BOARD. The Furnace or HEAT relay closes. The FURNACE has TWO wires.  When the TWO WIRES in the Control Box are JOINTED (Think of the relay as a LIGHT SWITCH), you TURN ON THE SWITCH.  When those two wires make a circuit....then the FURNACE starts.  There is NO 12 VDC signal.  Just the Control Board closing a contact and then the Furnace TAKES over. 

That's it.  Do you have a BAD module? Who KNOWS?? DO the above.  THEN test.  ODDS ARE (more than 90% of the issues and that is well over 100 members or folks saying...I LOST A ZONE...are in the RJ connections.  I had to clean mine THREE times...and I "know how" one time.  That is when I ordered NEW connectors...but that was 4 years ago and all is well.  GO FIGURE.  Thus, we have less than 10 BAD BOARDS or CONTROL Modules.  YES, they BREAK.  BUT, the issue is in the connection...and if there is the tiniest gap...and it vibrates...the Thermostat "forgets" who's their buddies.

In addition, if one never does the RESET...then that will make this happen.  Dometic says...RESET every time an RJ cable is disconnected.  RESETTING is the FIRST STEP after install.  The Thermostat has NO IDEA how many controllers are out there and how they are configured (some with HEAT and some without) and the NAME (zone 1 or 2 or 3.

Good Luck.  Let us know.  I would NOT REPLACE anything until you properly clean and reset, per the Dometic Protocol.

Let us know.

Tom,

Thanks for the in-depth trouble shooting guide. When this started happening, while we were on a trip a couple of weeks ago, I started searching the "knowledge bank" here and elsewhere for some guidance. Cleaning the RJ11 connections as you described was the first thing I tried, with the exception on the one(s) that connect to the control board up on the roof. I will go back and do that again, check the wires at the plugs, and replace the in-line connectors. If there is a bad plug, I've got spares and a crimper from when I installed a solar system. I misspoke/made an incomplete statement when I mentioned turning the switch at the bottom of the thermostat off and on. I turned it off and on in conjunction with the "reboot" procedure. Other than for rebooting, I don't touch the switch, because of previous warnings about fragility. The reset/reboot is what gets the unit working again after it shuts off.

You've answered my question about the furnace board- Thank you!

As I mentioned, the heat here in Maryland has been awful. Six o'clock this morning it was 82, and the humidity was 90%, which is too warm for me to go up on the roof. When there is a break, I'll plan on going up before the sun is up and cleaning the contacts on the roof unit. Because of the variability of the shutdowns being between 20 minutes, and three and 3.5 hours, I won't get a chance to really test things until we head out on our next trip at the end of the month. Since I don't want to deal with a failure while we're on a trip with family, I'm planning on also replacing the control board while I'm up there since I already have it. I will be keeping the old one to maybe swap out later. 

I will advise of success or failure to correct the problem.

Thanks again!

AlanC2

02 Windsor PST

 

 

9 hours ago, MyronTruex said:

Replace the inline couplers as a possible source of issues as well. After cleaning mine a few times and chasing ghosts I just replaced them and tore the old ones apart for inspection. I found corrosion and some questionable connections inside. They live in the updraft area and where I live there is tons of moisture in the air. And at 15 yrs old, they have vibrated constantly and outlived two air conditioners. 

Myron,

Thank you for the suggestion! I have new ones on order.

AlanC2

02 Windsor PST

 

7 hours ago, Dr4Film said:

The last time I had a similar experience on my 02 Windsor with the rear AC not showing on the 10 Button CCC-2 was because of a bad in-line connector.

I tested all of the data lines with my Sperry Instruments cable tester and eventually found the bad in-line connector.

Thank you Richard. I'll be going back to reclean connections, check wiring to the plugs/replace plugs if needed, and replace connectors.

AlanC2

02 Windsor PST

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1 hour ago, AlanC2 said:

Tom,

Thanks for the in-depth trouble shooting guide. When this started happening, while we were on a trip a couple of weeks ago, I started searching the "knowledge bank" here and elsewhere for some guidance. Cleaning the RJ11 connections as you described was the first thing I tried, with the exception on the one(s) that connect to the control board up on the roof. I will go back and do that again, check the wires at the plugs, and replace the in-line connectors. If there is a bad plug, I've got spares and a crimper from when I installed a solar system. I misspoke/made an incomplete statement when I mentioned turning the switch at the bottom of the thermostat off and on. I turned it off and on in conjunction with the "reboot" procedure. Other than for rebooting, I don't touch the switch, because of previous warnings about fragility. The reset/reboot is what gets the unit working again after it shuts off.

You've answered my question about the furnace board- Thank you!

As I mentioned, the heat here in Maryland has been awful. Six o'clock this morning it was 82, and the humidity was 90%, which is too warm for me to go up on the roof. When there is a break, I'll plan on going up before the sun is up and cleaning the contacts on the roof unit. Because of the variability of the shutdowns being between 20 minutes, and three and 3.5 hours, I won't get a chance to really test things until we head out on our next trip at the end of the month. Since I don't want to deal with a failure while we're on a trip with family, I'm planning on also replacing the control board while I'm up there since I already have it. I will be keeping the old one to maybe swap out later. 

I will advise of success or failure to correct the problem.

Thanks again!

AlanC2

02 Windsor PST

 

 

Myron,

Thank you for the suggestion! I have new ones on order.

AlanC2

02 Windsor PST

 

Alan and I talked.  Now understand how his system is configured...and he understands more about the MPX system and the connections and such.  He has several "Try this FIRST" options now.  Maybe a Data Cable connection...but when we say 90% of them is the cause...the other are in the Board.

FWIW, he had a REAR thermostat.  Thus his Zone1 is the REAR.  That always works.  His Front is Zone 2.  SO, he will try some things like swapping the "Danglers" up front.  and if that doesn't fix it...then odds are...a bad board. BUT if it runs great up there....on both side...then odds are a communications or data cable break between the Front and the Rear.  

He will be reporting back and posting or calling me.

He said THANKS for all the suggestions and comments and now has a much better understanding of the concept.

That's it...

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