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Randall
Randall, RVIA Certification
Category: RV
Satisfied Customers: 10335
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
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We are the 2nd owner of a 28' Enclosed Trailer with a

Customer Question

We are the 2nd owner of a 28' Enclosed Trailer with a Dometic ductlless roof air (and supposedly heat strip). It has a Dometic Digital Thermostat with 10 buttons (On/Off, Time, Clock, Zone, Mode, Program (all on the left side of the digital display). On the right side are the up & down arrows, Inside Temp, then the Fahrenheit & Celsius). The first owner bought the trailer new in 2012 and used it only twice. It has been garaged until now. On my first attempt to turn on the unit, the trailer was hooked to a generator. I received an E1 error code on the thermostat. I found the owner's manual online and cleared the E1. However, the unit will still not turn on and the Zone 1 button flashes. We replaced the 12V battery with a new one today. Disconnected all power for 30 minutes. After reconnecting power the Zone 1 button still flashes and nothing will turn on, not even the fan. I can see that the Zone 4 button is available, but the thermostat will not let me change Zones. Any thoughts?
Submitted: 6 months ago.
Category: RV
Expert:  Randall replied 6 months ago.

Two things...........is the thermostat configured correctly and is it programmed correctly? Do you have the User's Guide for this or not?

Customer: replied 6 months ago.
I found a Dometic Comfort Control Center 2 Thermostat User's Guide online. "Is the thermostat configured correctly" and "Is it programmed correctly"? I have been through the guide step by step (only 8 steps). This is my action and result, if any to each step.
1. How to wake up the thermostat and turn it on. Done.
2. Mode Button - Used to cycle through the modes. My available modes (Off, Cool, Fan). I am able to cycle through them, but the unit still does not come on...not even the fan. My seller indicated that the unit has a heat strip. I do not have HS as an option.
3. Zone. Press the Zone button to cycle through the zones to be programmed. I cannot cycle to any other Zone. My thermostat displays Zone 1 (which is flashing) and Zone 4 (but, I cannot select it).
4. Up/Down Arrow Buttons - On the Cool setting, I was able to adjust the room temp (aka, the set-point).
5. Fan. When pressing the Fan Button, I can adjust to Auto, Lo, Med, High on the thermostat, but the unit does not turn on.
6. Clock. I am able to set the clock.
7. Inside Temp. Prior to the reset of the E1 Error Code, I was able to see the inside temp. An inside temp no longer displays. Online I found a Dometic Owner's Manual with instructions on how to reset the E1 Error Code: From the Off Setting, Press & Hold the Zone and Mode Buttons. INIT will appear. Then press the On/Off button and the available Zones will appear. This occurs after the reset; however, now Zone 1 is flashing and nothing is still happening including being able to change Zones.
STEP 8. Outside Temp - I do not have this button.Programs Button - when I select the Programs button, I am able to switch between Program 1 and Program 2, as well as change the time. There was nothing in the User's Guide about programming them. Also, I do not need it to be programmed, if it doesn't have to be. We use this trailer on the weekends for racing and do not need it to run at specific times. However, in one of my many attempts to turn on the unit, I set the Program times to be consistent with the actual current time, but it did not help. I have not adjusted it to be consistent with the other attempt times since the new battery install.
Thank you for any guidance you can offer.
Expert:  Randall replied 6 months ago.

Was this working before? Did you set it up to work on Zone 1 or not?

Expert:  Randall replied 6 months ago.

Did anyone mess with the dip switches on the control box or were they ever set? That may be the problem, unless this was working before and nobody touched those.

Customer: replied 6 months ago.
We do not know if it was ever set up. The previous owner purchased it for his son. He believes the son used it. Since it was purchased new from a dealer, we assumed it was set up before leaving the lot. We have not messed with the dip switches or control box.
Expert:  Randall replied 6 months ago.

Then that would be the first place to check. The dip switches on the control board may not be set correctly. Those are on the A/C itself. Depending on the model you have, there will be either a silver colored control box on the bottom of the A/C OR just a control board up on top of the A/C. The box has a small cover that you remove to access the dip switches. There are 10 of them. Check that and see which ones are on. The box will be under the ceiling grill where the return air is and filter (if you have that model) or up on top on the side of the A/C and that can be accessed when you remove the A/C shroud. Let me know what you have.

Customer: replied 6 months ago.
We found the Control Box on the top side. When facing the panel, all switches are thrown to the left (not sure if that is off or on) except #7. I attached a photo.
Switch #1 - Exit Stage
Switch #2 - Zone 2
Switch #3 - Zone 3
Switch #4 - Zone 4
Switch #5 - Stage
Switch #6 - Heat Strip
Switch #7 - Heat Pump (This switch was thrown to the right)
Switch #8 - Furnace
Switch #9 - Dehumidifier
Switch #10 - General Start
We found some #'s on the unit that may be of use to you.
Mfg# *****
Product####-##-####Serial# *****
SKU#(###) ###-####Thanks so much for walking us through this.
Expert:  Randall replied 6 months ago.

You are welcome! Yes, that is the problem. Turn on #1 and #8 which should be the furnace. Then try it. I don't think you need #5, but I can check on that for you. Good information you sent! Wish all my customers were as through!

Customer: replied 6 months ago.
We'll switch #1 & #8 to on. All other switches should be off, we'll do that, too.
Customer: replied 6 months ago.
We adjusted the switches accordingly and have disconnected all power from the thermostat. We'll wait 20 minutes to re-establish power to the thermostat, hoping this resets everything. When we reconnect, we will be attached to a new and fully charged 12V battery and the generator will be on.
When you get back to me about Switch#5, can you also let me know how I can determine if we have the heat strip, since HS was not a previous Mode option offered. Maybe it will be now that we are moving Switch#8 to on. I might be asking this question prematurely. I'm glad we consulted you, I would not have guessed that #8 Furnace would be in On position, I would have thought #6 Heat Strip.
Customer: replied 6 months ago.
Hit send too soon... I would not have guessed that #8 Furnace would be in On position, I would have thought #6 Heat Strip, as we do not have ducts.
Customer: replied 6 months ago.
We switched #1 (Ext Stage) & #8 (Furnace) to On. We switched #7 (Heat Pump) to Off. Unplugged the thermostat from power, waited a half hour. Turned on the generator, reconnected the thermostat to 12V power. Nothing had changed, unit will still not turn on and Zone 1 is still flashing. I also find it odd that we have one AC unit, but the digital display shows Zone 1 and Zone 4 (Zone 4 is not blinking). I am unable to switch between the Zones with the Zone button. If I use the power button on the thermostat to turn off the thermostat, I can get an inside temperature reading by pressing the button. If I have the thermostat turned on, when I press the inside temperature button, the temperature is 00, but also it shows only zone 4 (not a blinking zone 1). All other Modes (Cool & Fan) show Zone 1 (blinking) and Zone 4 (solid).
Lastly, if at any time I press the program button, I am unable to get out of the programs (program 1 and program 2). I can toggle between the two programs, but am unable to get out of it...not even by pushing the Mode button. The only way I have been able to get back is to do the reset (When thermostat is off, hold down zone and mode, then turn on thermostat).
We called the previous owner and he said that the unit had been working prior to the trailer going into storage.
Expert:  Randall replied 6 months ago.

Sorry for the delay in getting back to you.............I was up in Oregon all day. Did you try re-booting the thermostat? I am wondering if it is working properly.

Customer: replied 6 months ago.
We have re-booted the thermostat multiple times today. We have gone as far as to take the thermostat cover off and unplug the "phone cord". Each time we put power back to it, same issue. Showing Zone 1 blinking and Zone 4 solid. We shouldn't even have 2 zones. After speaking with the previous owner, who indicated the unit worked before storing, we put the dip switches back to their previous settings. After inspection, my husband said it does not have the heat strip it has a heat pump, which now explains why Switch#7 was on. Any additional ideas?
Expert:  Randall replied 6 months ago.

I think either the thermostat or control board is bad, but let me call Dometic in the morning and ask them to be sure. I am in California and it may be 9 or 10 my time before I get through. I will get back to you with an answer.

Expert:  Randall replied 6 months ago.

Sorry for the delay in getting back to you. My wife had her family out here from Florida all last week. Let me call Dometic Technical line and see if they can shed some light on this.

Customer: replied 6 months ago.
When we didn't hear back from you, we thought you had given up on it. We took it to a service center on Friday.
Expert:  Randall replied 6 months ago.

Don't blame you a bit..........sorry for the delay. Hope they got it figured out for you.