Front rooftop hvac issues -2007 diplomat

[Coach J]

I have a Dometic rooftop ac/heat pump that will not stay running long enough to reach the desired temperature. It seems to be worse when temperatures outside are higher but that could be a pure coincidence 

 

example:  I set the thermostat to 70 and it is 75 in the coach and the AC turns off. Not just the compressor but the entire unit. Back AC runs like a champ but front one has been having this issue for a while I think. When the compressor comes on it is blowing at about 22 degrees colder than intake temp but it just won’t stay running. 
 

any ideas???

 

thank you 

[Ivylog]

Try using 68 instead of 70.

[Coach J]

Just now, Ivylog said:

Try using 68 instead of 70.

I have tried 68,65,60 etc 

[cbr046]

low freon.  You can replace the whole unit or have a tech charge it up (cheaper option).

- bob

[FishAR]

Check where the temp sensor is for your front ac and make sure a duct isn't blowing directly on it. If it is re-aim the duct away from the sensor.

[Coach J]

3 minutes ago, FishAR said:

Check where the temp sensor is for your front ac and make sure a duct isn't blowing directly on it. If it is re-aim the duct away from the sensor.

Weird enough you say that. The sensor is near the front door. Every time I open the door the AC unit turns off 

[Tom Cherry]

15 minutes ago, Coach J said:

Weird enough you say that. The sensor is near the front door. Every time I open the door the AC unit turns off 

Most of the HVAC systems use the thermostat as the sensor.  You have a wall sensor (brown cage) in the rear.  Only, typically, does the front zone have a remote sensor.

Please post a picture of your thermostat and what you are calling the front sensor

Thanks

[Ivylog]

35 minutes ago, Coach J said:

I have tried 68,65,60 etc 

Find the remote tem sensor and make sure it’s not touching anything.

[Tom Cherry]

19 minutes ago, Ivylog said:

Find the remote tem sensor and make sure it’s not touching anything.

Per the manual, page 95, there is no front temp sensor.  The 5 button thermostat has the built in temp sensor and controls all zone 1 or front HVAC systems.  There is a picture of a remote temp sensor, but it is for the rear or zone 2.

i do not believe, unless the OEM system was replaced with a different system that there is a front sensor….but one never knows.

Really need verification and pictures before going down that trouble shooting path…

If the front unit is not running, then there may be a mechanical issue.  The fact that he has good communication with the rear or zone 2 says no probable issues with the thermostat or communication.

Based on the age and many posts recently….odds are motor or compressor or “control issues” in the front.  My experience is that it takes a day or two from the “walls” to equalize…..but eventually, the interior walls will come close to the set point of the thermostat.  I have a surface mounted sensor above the thermostat…..it is within, on normal days, a degree of the set point.

.  

[MrAmbassador]

Agree with the above, low on Freon and shutting down on low evaporator temp (sensor) or front ambient temperature sensor is faulty or air vent blowing on it. Do you have a Dometic 10 button thermostat, if so you can check the inside temperatures in zone 1 and 2. If you are low on Freon you would need to check your running amps to check the load (you will need an amp hook/claw/ring). 

[Coach J]

35 minutes ago, Tom Cherry said:

Most of the HVAC systems use the thermostat as the sensor.  You have a wall sensor (brown cage) in the rear.  Only, typically, does the front zone have a remote sensor.

Please post a picture of your thermostat and what you are calling the front sensor

Thanks

 

18 minutes ago, Tom Cherry said:

Per the manual, page 95, there is no front temp sensor.  The 5 button thermostat has the built in temp sensor and controls all zone 1 or front HVAC systems.  There is a picture of a remote temp sensor, but it is for the rear or zone 2.

i do not believe, unless the OEM system was replaced with a different system that there is a front sensor….but one never knows.

Really need verification and pictures before going down that trouble shooting path…

If the front unit is not running, then there may be a mechanical issue.  The fact that he has good communication with the rear or zone 2 says no probable issues with the thermostat or communication.

Based on the age and many posts recently….odds are motor or compressor or “control issues” in the front.  My experience is that it takes a day or two from the “walls” to equalize…..but eventually, the interior walls will come close to the set point of the thermostat.  I have a surface mounted sensor above the thermostat…..it is within, on normal days, a degree of the set point.

.  

The pictures are the front sensor. There is one in the back also. The outside temperature has cooled down a few degrees and it seems to be working correctly for the time being 

4 minutes ago, MrAmbassador said:

Agree with the above, low on Freon and shutting down on low evaporator temp (sensor) or front ambient temperature sensor is faulty or air vent blowing on it. Do you have a Dometic 10 button thermostat, if so you can check the inside temperatures in zone 1 and 2. If you are low on Freon you would need to check your running amps to check the load (you will need an amp hook/claw/ring). 

No a 5 button system. 

[MrAmbassador]

Yes sir that is a front temp sensor or zone 1. Aim a hair dryer on it about 10 inches away and see if the AC starts and remains running. 

[klcdenver]

Tom not to bust your chops but the 2007 Diplomat does have 2 temp sensors. The front one is right behind the passenger window just like the picture he posted. 
 

I would go up top and remove the shroud and wash out the coils with a water hose. Also check the inside of the shroud to make sure it has foam pressing against the top of the coils to separate intake and discharge air. Sounds like it is getting hot and the over temp switch is shutting it down. You might also do a hard reset on the 5 button thermostat control.

You should also check the coils to see if it is freezing up. When it shuts down remove the inside white box from the ceiling and see if those coils are froze over. There is also a thermostat with a brown wire on it and it should be stuck in those coils also. They are notorious for falling out.

[Coach J]

18 minutes ago, klcdenver said:

Tom not to bust your chops but the 2007 Diplomat does have 2 temp sensors. The front one is right behind the passenger window just like the picture he posted. 
 

I would go up top and remove the shroud and wash out the coils with a water hose. Also check the inside of the shroud to make sure it has foam pressing against the top of the coils to separate intake and discharge air. Sounds like it is getting hot and the over temp switch is shutting it down. You might also do a hard reset on the 5 button thermostat control.

You should also check the coils to see if it is freezing up. When it shuts down remove the inside white box from the ceiling and see if those coils are froze over. There is also a thermostat with a brown wire on it and it should be stuck in those coils also. They are notorious for falling out.

I will start to look into those things tomorrow. Would your assumption that it may be overheating be worse when outside temps are higher?  I am assuming yes. 

22 minutes ago, klcdenver said:

Tom not to bust your chops but the 2007 Diplomat does have 2 temp sensors. The front one is right behind the passenger window just like the picture he posted. 
 

I would go up top and remove the shroud and wash out the coils with a water hose. Also check the inside of the shroud to make sure it has foam pressing against the top of the coils to separate intake and discharge air. Sounds like it is getting hot and the over temp switch is shutting it down. You might also do a hard reset on the 5 button thermostat control.

You should also check the coils to see if it is freezing up. When it shuts down remove the inside white box from the ceiling and see if those coils are froze over. There is also a thermostat with a brown wire on it and it should be stuck in those coils also. They are notorious for falling out.

Upon initial inspection from just opening up the inside cover there is a decent amount of dust build up. I had the outside unit serviced aboit 3 months ago but the coils and most of the unit was fairly clean at that time. I will go back up and inspect tomorrow.  
 

mind if I keep in contact 

[Gary Cole]

If you have a 22 degree temp differential you don't have compressor problems when it is running. Which rules out a low charge or a worn compressor. Could still have a winding problem causing overheat though unlikely with the symptoms you describe. You can jump the contactor from inside bypassing all control circuits but the high temp limit on the compressor to check the condensing unit. 

Edited May 29, 2023 by Gary Cole

[Coach J]

8 hours ago, Gary Cole said:

If you have a 22 degree temp differential you don't have compressor problems when it is running. Which rules out a low charge or a worn compressor. Could still have a winding problem causing overheat though unlikely with the symptoms you describe. You can jump the contactor from inside bypassing all control circuits but the high temp limit on the compressor to check the condensing unit. 

I do have anywhere from 20-23 degrees difference when running. Only issues seem to be when the outside heat gets up high. 

[Tom Cherry]

35 minutes ago, Coach J said:

I do have anywhere from 20-23 degrees difference when running. Only issues seem to be when the outside heat gets up high. 

Fascinating.  The manual talks about the thermostat controlling and sending a signal to the system and showing a remote.  So you have two remotes.  Must have been something to do with where the thermostat is located and how the “control panel” where it is located.  Typically, in the upper end coaches that had up front remotes, they were sometimes under a cabinet.

i would recommend that you pull the cover off the up front sensor.  We have had a few instances where the assembler buried or pushed back the sensor or almost blocked it and the differential was an issue.  Most of us, but now i know, not all of us, with the front unit being controlled by the internal temp sensor in the thermostat don’t have this issue…..as to the set vs the actual temperature or comfort.  An exterior wall sensor is a poor design, but hey, this is Monaco.

OK….next comment, based on your statement….”every time i open the front door, it shuts off”. I hasten to speculate on that, but if you have the prints, find the HVAC print.  Either snap a photo or scan it and post it.  The way the system works if this.  There is a main or actually a “brain” inside each AC unit.  The thermostat is not exactly totally dumb…..but it only acts like a gate keeper.  Since you have two remote sensors, the front and the rear HVAC units are configured the same, as far as temperature control goes.  The controller has the AC incoming and sends AC to the compressor/fan.  There is also a pair of phone or communications cables.  The thermostat is on the end of a continuous loop.  There is a phone line running from the thermostat to the front unit.  Then that lines goes into and out of the controller.  The phone connectors are not polarized…so it doesn’t matter.  The outgoing communications cable then connects to a data (phone) line that goes to the rear.  Then the signal goes into the control module….there is an outgoing phone connection just like up front.  But this is the end of the line….so it just hangs there, unused.

When a system is installed, it has to be “booted” up.  With the thermostat switch OFF, holding in the Zone & Mode buttons snd turning on the switch boots it up.  That tells the “gatekeeper” thermostat who is “playing”….  In your case, it is told that you have 2 zones and the front one is delineated, via a DIP switch as Zone 1. Since there is a remote sensor wired into its controller, just like the back, the thermostat is told….use this one and NOT its on.  I don’t know if you have one or two furnaces….but if you have 2, then the DIP will be set for furnace on both.  THEN….the thermostat starts calling the shots and is the gate keeper.  But each of the control modules in each HVAC actually does the work…

OK….all of that might  seem a bit over the top or way too complicated or why do i need to know how to build a watch…? All i care about is the time…

Here is a random thought.  If for some reason, and i can’t explain it and without a print and this being a very non typical scenario, IF…and I say IF….there is a an issue with the wiring from the remote sensor (it is HARD WIRED….think of it being a light switch….) then there will be issue.  The remote sensor is like a light switch.  When it is on or closed and the system is running….if you “open” it (as in the temperature causes the sensor to OPEN or be off), that immediately shuts off the unitnitnis controlling.  Same for closing.  I have NO idea where Monaco ran the single pair (2 wire) cable or line from the remote sensor to get to the front HVAC controller, but it has to get there.  It does NOT run to the thermostat.  There is only a 4 wire communication (RJ11 Phone) connection of the thermostat…

I personally would get the PN from the control unit and download the wiring and installation instructions.  If the front unit is a 13.5KW, then the control unit is accessible from the interior….remove the filter grill and you will find it,  if it is a 15KW unit, you have to pull the cover off the outside unit and that is where it lives.

There will be (memory) three sets or pairs of wires.  One is AC….  There will be a pair of Furnace leads….  There will be, since you have a remote sensor, a pair of wires for it.  I would unhook the remote sensor wires….they do NOT carry voltage….but just for safety, either put on a wire nut or tape.

NOW….you will have to reboot or reset the system.  Thermostat switch off.  Hold in zone and mode….switch on.  FF should appear and go away.  NOW, the thermostat has been told “there is NO remote sensor” so the temp sensor in the thermostat controls Zone 1 or the front. NOW see how it works.

FWIW…i HOPE this is not the case….it means there is a wiring issue.  BUT.  If that is the case, then you purchase a NEW sensor and mount it about 6 - 8” away from where the filter cover goes and then spray the brown cover white and move on.  OR, you abandon the front remote and see how it works and controls.  Pulling wire or such is not an option, unless you are Harry Houdini….  I really don’t know if you can pull enough wire out of the wall to cut and splice in a new sensor….but we rarely….never say never…have a bad remote.

That’s my take from what you said.  NOW, if Monaco devised some relay system and for what ever reason, wanted the HVAC to shut down when you opened the door…then it SHOULD be on your prints….I don’t have that.

Other 07 Diplomat owners will have to chime in

Let us know…and do some testing and troubleshooting.  

[Tom Cherry]

1 hour ago, Coach J said:

I do have anywhere from 20-23 degrees difference when running. Only issues seem to be when the outside heat gets up high. 

From a "Rule of Thumb" standpoint.  That's a bit too high.  If you make sure that the filters are cleaned....and they get dirtier way faster than you realize....you should be closer to 20....  but, generally speaking, that means that the AC is working. 

I still, after some "noodling time" believe you have a wiring issue or a problem with the front Remote.  The clue to me....assuming the someone did not get really cutesy at Monaco and try to wire in an "Open Door" relay with the sensor....and they would have had to cut into the OEM Factory cable that came with the sensor...is just that...  A wiring problem or a defective sensor...

That is the ONLY logic that would make the HVAC cut off when you opened the front door...and, with running a chance of getting my chops busted again....we have NOT, EVER, NEVER seen this....but who knows.

Bypass the Remote per my instructions and see if that fixes it....otherwise you will need a tech....I think

[klcdenver]

Here is a trouble shooting guide.

Air conditioner troubleshooting.pdf

[Tom Cherry]

2 hours ago, klcdenver said:

Here is a trouble shooting guide.

Air conditioner troubleshooting.pdf 6.62 MB · 3 downloads

THANKS….a big help.  You also sent me a print that makes sense.  NOT one of Monaco’s better versions as it does the silly (to me) pin to pin logic….and I don’t do well with them.  
 

OK, @Coach J  

here is what this explains if you need some “help”.  The diagram shows that there are 2 remotes.  If you “open and inspect” the front control unit, the remote sensor (memory was short….is NOT a large or 18 gauge two wire cable)…it is a Phone Cable.  Look on the print.  It is labeled as P4..PHONE.  So, your quest just got easier.  

There are only 2 OTHER phone lines….coming from the control unit and, if you trace them, they are connected to the dual inline RJ11 connections….so, you got 3 phones lines in the control box and two go out to the connectors.

IF you then unplug that one….you have removed the remote.  Then you do the reboot or reset.  Try it then….if it still cuts off and acts funny….then time for a tech.  You have got eliminate variables…..and the funky shutting off when you open is NOT a feature that was OEM.  Folks have had issues with the communication cable.  Monaco would drive in a screw or a wire (cabinet or whatever) staple or they would pull hard and nick a wire….or something was put over the phone cable and eventually nicked it or crushed it….bingo….intermittent issues like you have….so, going back to using the temp sensor or thermistor in the thermostat eliminates that..

One final thing…..get the thermostat working without the remote.  Verify all is well.  If, by chance, there was a loose phone connection, then plug it back in (take a picture) and reboot and try it.  You never know as this is a funky Multiplexed signal and that is the cause of 90% of the issues….a bad communication issue….

Let us know…..
 

Air%20Conditioners%20wiring%20diagram.pdf

[Coach J]

Ok. Not sure what is going on but we will see. 
 

I ran the front AC all day yesterday after moving the air vent off the remote sensor and covering it up with the window curtains. AC has run all the time and had the temperature down to 65 and never shut off. Will monitor and get back with this group as it moves forward. Didn’t want to jump too deep into doing things that may be over my head. 
 

as always thank you for all the input and help. 
 

[Gary Cole]

Great if it is something that simple. I re-read your post and your observation that the unit shuts down normally, i.e. compressor and evaporator fan together means that the board is receiving a command to shut down. I'm not really familiar with these units other than having to replace a freeze control sensor one time. However I'm thinking after looking at Tom's information that the only 2 inputs which shut the unit down in normal fashion is  the remote sensor which over-rides the primary enable command from the thermostat and the thermostat itself. The ambient temperature sensor is related to heat pump mode.  The freeze sensor shuts the compressor down however keeps the evaporator fan running in order to defrost the coil. This is assuming your board and thermostat are good of course. There are a couple of people on this forum  here who do know a lot about AC and these units. 

Edited May 30, 2023 by Gary Cole

[Tom Cherry]

1 hour ago, Coach J said:

Ok. Not sure what is going on but we will see. 
 

I ran the front AC all day yesterday after moving the air vent off the remote sensor and covering it up with the window curtains. AC has run all the time and had the temperature down to 65 and never shut off. Will monitor and get back with this group as it moves forward. Didn’t want to jump too deep into doing things that may be over my head. 
 

as always thank you for all the input and help. 
 

That is absolutely WONDERFUL.  Sounds like the sensor is working.  HOWSOMEVER.... I'm trying to muddle through this.  You reaimed the outlet that was blowing directly to the sensor.  That means that the cool air ( 70 Deg Ambient inside the MH MINUS the 22 Deg Delta T....or 58 Deg) was turning OFF the remote.  Since we don't know how FAR the Remote is from the air duct....then that 58 Deg will go up...but NOT enough for the various set points that you tried.

OK....Next up....When you cover up the remote sensor, you are really blocking it.  NOW....that may be a GOOD or BAD thing.  When the HVAC was blowing on it...you said that the Unit never would cool down to your needs....and you set it several degrees lower....(Paraphrasing).  OK...now the ball is in your court.  There are two things wrong (Thank Monaco....not our fault).  The Sensor is on an Outside Wall.  A REAL NO NO... YES, there is insulation in the wall...but you still get some radiant heat (or cooling).  Remotes are supposed to be on an INTERIOR wall so they will not be impacted or affected by the heat or cold coming through insulation.

You can experiment....The curtain will diffuse the air...and maybe provide a more "ambient" temperature.  BUT, it can also, theoretically, TRAP stagnant air.  Traditionally, covering up a Sensor is NOT a good idea. There are no "small" Thermostat (clear boxes) that would look or do OK (my opinion) that you could install.  The clear AC vent deflectors are too big (10" minimum).  My advise would be to play with it.  See if you can adjust the vent where it is NOT blowing directly on the remote and leave the curtain out of the picture.  ONE solution....totally OFF the wall.   You can purchase a large SS Wire Mesh filter for a garbage disposal.  They also come in different sizes.  IF you used a piece of cheese cloth or a loose weave and made a simple cover for the bowl of one of these, it could be mounted OVER the present (or remove it) cover.  That would diffuse the air and let the area be MORE at Ambient...  Just a comment.  KISS is what you need.

OK....getting past the above.  I am STILL a bit confused by the info you posted....

Weird enough you say that. The sensor is near the front door. Every time I open the door the AC unit turns off 

I don't QUITE understand that.  When you open the door, you would get a pressure as well as an air change inside.  If the Unit was running and you had it in COOL....then YES....the sensor would change....how quickly.... I do NOT know.  The tip of the sensor behind the cover has to change and that takes a little while.  If you put a hair dryer on it to bring ON the heat....you would know how fast.

SO....when you moved the air vent and covered the sensor....does the AC cut off when you open the door.

That is the only missing piece to what your problem is....and there are probably more than one of us that can't wrap our heads around the OPEN DOOR....AC CUTS OFF.

Can you expand or clarify that for us....

Thanks....

 

[Bill R]

I had a similar issue with my remote sensor in the same location by the door.    When the sun would be shining on that same side, the wall would become warm and cause the sensor to read a higher than the inside temp and keep the AC continuously running.  I would have to change the set point on the thermostat about 7 degrees higher when this happened and then readjust when the sun moved.  
This became a tedious exercise, so I relocated the sensor and mounted it on the return air grille frame on the opposite side of the air intake side.  I just found the sensor line in the intake plenum and spliced the sensor into that.   Now my AC kicks on and off at exactly the same temp readout on the thermostat.   So much better now.  

[96 EVO]

3 hours ago, Bill R said:

I had a similar issue with my remote sensor in the same location by the door.    When the sun would be shining on that same side, the wall would become warm and cause the sensor to read a higher than the inside temp and keep the AC continuously running.  I would have to change the set point on the thermostat about 7 degrees higher when this happened and then readjust when the sun moved.  
 

That's what I would expect to see with the remote sensor mounted there, but the OP was having the opposite problem, with his AC shutting down early 🤔.