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RVDreamer · 08-10-2016, 09:25 PM

I have a 2015 27FB International Serenity. I ordered the trailer new with dual A/C units for the front and rear zones.

Since the trailer was new, neither temperature sensor has accurately responded to the indoor temperature. This results in the thermostat being useless because it doesn't accurately read the temperature change of the interior zone.

I suspect that the problem is the location of the temperature sensors. There must be two, one for the front and one for the rear because they read different temperatures from each other. But both are inside the interior skin and must be too heavily influenced by the exterior skin temp.

For example, while in Vegas the outside temp was 110+ all week. I had the A/C thermostat for both zones set at 72. However the inside temp according to the thermostat never dropped below 85. In reality, the inside temp was probably in the mid 60s. It was freezing us out. Since the inside temp according to the thermostat never dropped below 85, the A/C ran continuously. If you turn the thermostat up to 86 then it gets too hot and the A/C doesn't turn on at a decent inside temperature because the sensors don't measure the correct inside temp.

I want to fix this problem but I am unsure where the temperature sensors are for the 27FB International Serenity with two factory A/Cs.

What have others done? Is there an easy fix? Does anyone know if there is a replacement thermostat that uses wireless sensors that could be placed somewhere in the interior of the cabin? Basically the current thermostat is useless for regulating heat or cold when the sensors are not accurately reporting the inside temperatures.

Hogfan · 08-10-2016, 09:57 PM

We have a 2015 International and we are having the same thing. The living room unit is freezing us out and the bedroom unit air output seems so much warmer. Nit hot, but not AC cold???

RVDreamer · 08-10-2016, 10:25 PM

That sounds like a different problem. Both our front and back ducts put out cold air just fine.

Our problem is that the thermostat sensors don't measure the indoor temp correctly.

I think the rear sensor might be up against the refrigerator unit, so it reads a nearly constant warm temperature. The other sensor in the front must be too close to the outside skin because it reads way too warm when the sun shines on the outside, when it is cold outside it reads way to cold.

Either way the thermostat works, and our air is cold, it just is impossible to regulate the correct temperature because the sensors are wrong.

I know they are way off because I can measure the inside temp and it is nothing like the inside temp being reported by the thermostat when you hold down the inside temp button.

No. 13 · 08-10-2016, 10:34 PM

Make sure the fan is set to auto

lewster · 08-10-2016, 10:35 PM

If you investigate the Dometic installation manuals, you will see that the mounting and location specifications for their remote temperature sensors are quite specific. Unfortunately, Airstream, (as they do so often) almost TOTALLY IGNORES these engineering details and places the sensors where ever they feel it's 'convenient'!

If I recall (it's been a while) the sensor should be located approx. 48" above floor level and not exposed to an outside window (excessive heat/cold) or near any other heat producing appliance.

I have seen these sensors placed on the wall that forms the fridge chimney (near the TV mount), which is also next to a nice, large window. What could possibly be wrong with THAT location???

You might not have an operational problem with the sensor, but rather with it's poor location!

RVDreamer · 08-10-2016, 10:58 PM

Hi Lewster,

I think it is just a location problem not a functional problem.

Both sensors read temperatures that change over time but just don't accurately reflect the real inside temp.

What is the best way to go about fixing this? How do I find the sensors and re-locate them to better locations?

It would be nice if there were a wireless solution that would allow you to place sensors in the interior. Similar to the way the new smart home thermostats allow you to place multiple battery powered sensors around in your home.

lewster · 08-10-2016, 11:44 PM

Unfortunately, you are limited to the use of Dometic's hard-wired remote sensors as they are proprietary to the control boards and CCC-II thermostat. I'm not sure if you can extend the cable by splicing more wire onto the existing sensor to relocate it.

A call to Dometic's tech support line might get you the answer for that.

Quote:

Originally Posted by RVDreamer

Hi Lewster,

I think it is just a location problem not a functional problem.

Both sensors read temperatures that change over time but just don't accurately reflect the real inside temp.

What is the best way to go about fixing this? How do I find the sensors and re-locate them to better locations?

It would be nice if there were a wireless solution that would allow you to place sensors in the interior. Similar to the way the new smart home thermostats allow you to place multiple battery powered sensors around in your home.

OTRA15 · 08-11-2016, 03:51 AM

Similar problems have been reported on a variety of threads, which these search results for "Dometic thermostat sensor location" will aid in finding FYI:

https://cse.google.com/cse?cx=011403...tion&gsc.sort=

For example, these threads may help:

http://www.airforums.com/forums/f427...ct-153524.html
http://www.airforums.com/forums/f427...ms-149418.html
http://www.airforums.com/forums/f427...or-148649.html

Or maybe some of the threads listed in this sub-forum:

http://www.airforums.com/forums/f427/

Good luck in relocating your sensors!

StokerDoc · 08-11-2016, 05:46 AM

I have a 2013 28' International Serenity with dual, non-ducted, A/Cs. The bedroom is Zone 1 and the main cabin is Zone 2 with the furnace being on Zone 2. The thermostat is in the bedroom.

I found the remote temperature sensor in the main cabin (zone 2) behind the TV. It is a small white vented cover. The weird thing is the remote sensor displays the main cabin temp, again, Zone 2, on Zone 1 on the thermostat. And vice versa for zone 2, it gets its temp information directly from the thermosta in the bedroom. I tested it. I took the cover off the sensor, held the sensor in my hand and saw the temperature change on Zone 1 on the thermostat display. I closed the curtain and had a small electric heater running in the bedroom and Zone 2 temp display rose accordingly, while the main cabin was quite cooler and the temp stayed constant as I left windows open on a chilly day.

So the A/C in the bedroom is controlled by the remote sensor in the main cabin, and the A/C in the main cabin is controlled by the temp in the bedroom. When the curtain is closed, like we do almost every night as the kids sleep in the main cabin, we have a hard time balancing the temperature in the trailer.

I'm baffled by this. Maybe someone could explain why this was done. I've had it looked into by my dealer, but he said all was as it should be.

OTRA15 · 08-11-2016, 05:54 AM

Are you sure the dealer knows his stuff? Sounds like the two sensor wires were installed backwards. Have you tried a hard reset of the stat per the Dometic manual with your AS paperwork? This is discussed in many threads including the ones I linked earlier. You may have a software glitch which the hard reset could fix IMO.

Good luck!

Peter

StokerDoc · 08-11-2016, 06:02 AM

I did a full reset, and I got into the service side of the thermostat and determined that there is no remote sensor connected on Zone 2. But there is on Zone 1. The sensor plugs into the AC as does the control for the furnace. A simple communication wire connects the 2 A/Cs and another communication wire connects the thermostat. For some reason it appears like the remote temp sensor is placed in the main cabin and plugged into the bedroom AC. Without pulling the interior ceiling skin down to confirm, I might add.

OTRA15 · 08-11-2016, 06:52 AM

Thanks. Hopefully lewster will have some suggestions for you.

jayseejay · 08-11-2016, 07:27 AM

Hi RV Dreamer-

This is a fairly common problem with the AC sensor placement in newer 27' units with 2 ACs. Zone 1 - the zone where the thermostat resides, is controlled by a sensor in the thermostat itself. Zone 2 is controlled from a sensor on the fridge was behind the TV in the living area. The heat from the fridge (and the TV if on) impacts the reading of the sensor (which is mounted in the small white plastic cage). Some of us have had luck improving the reading by pulling the wire sensor out a few inches from the mounting hole so it reads more of the ambient air temperature, but it still reads 5-8 degrees too high, so we set that zone higher at the thermostat by about that amount. (I'm not sure why your zone 1 sensors is not reading well. Perhaps heat from a bedroom tv is reaching the thermostat?) Hope that helps a bit. Joe

m.hony · 08-11-2016, 11:56 AM

I think the sensor for the front unit is within the thermostat housing.
The sensor for the bedroom unit in my trailer is on the wall near the TV, so the heat from the TV causes the unit to run constantly and freeze you out of the bedroom.
I have voice my general annoyance with the CCC II thermostat system. No need to rant here.
Basically, though, this system is a useless, unreliable, overly complicated POS!

Krusty Buns · 08-11-2016, 12:37 PM

We have a 2013 Intnl Serenity w/ 2 A/C (bought new). I would swear the sensors and zones are reversed based on performance, but had the dealer near Austin check and... no problem found (no problem for them). We keep a good fan going all the time to try and get a constant temp throughout the unit. Major fail for Airstream considering the cost of a new unit.

turk123 · 08-11-2016, 12:54 PM

I noticed in my air return vent (one of two / single ac unit) that there is a senser in the vent behind the screens. My unit reports air temp in. Maybe this is different than the room temp. If it is the same, I can see why it would have a problem on very hot days.

Mine is a 2017 27fb.

jcwall · 08-11-2016, 02:08 PM

All good replies. The sensor for the bedroom is located in the thermostat. The one for the rear is located behind a small round white plastic cover behind the TV. If you use the diagnostic mode on the thermostat you can check the remote sensor and see if it is giving an accurate reading. Unfortunately Airstream attaches the tip of the remote sensor to the wall with a small plastic clip. As a result it is measuring the temperature of the wall and not the air. This is bad because the wall abuts the refrigerator and can get quite hot. Thus the AC unit thinks the air temperature is 85 degrees and keeps pumping out cold air. I've had mine set at 78 degrees and come into the trailer and found the air temperature to be 68 degrees. It just doesn't shut off. My fix was to take off the white cover, make a small hole in it, put in a rubber grommet and bring the tip of the sensor out so that it is waving the the air. I cannot help that it is next to a window or adjacent to the TV but it works a lot better.

RVDreamer · 08-11-2016, 03:16 PM

Thanks for the great suggestions and info.

I will have to dig into this further when I get time and come up with a solution.

Has anyone tried to just ditch the current thermostat and replace it with something like a Ecobee 3 Smart thermostat?

I know it is expensive but it would be nice to be able to monitor temp via the internet while away from the trailer. Also the Ecobee 3 has remote battery powered sensors that can be placed anywhere to control the thermostat.

I am not sure this is even possible with the control wiring that exists for the A/C and furnace.

m.hony · 08-11-2016, 03:45 PM

The Ecobee thermostat may or may not work with the Dometic units- proprietary BS-

Candace · 08-12-2016, 10:10 AM

We have a 2013 FC 27ft, same problems. Finally at the factory last year we got the service tech to move the sensor from behind the TV to up to the top of the wall. [they were doing some work that required removal of Fridge, so it was easy for them to do]. And the tip hangs out now about 4 inches from the white cap. It still is hot up there, but it is much easier to control the cabin temp that it was before. Evidently there was plenty of wire in there to enable them to move it up. We recommend that, at least it gives the owner a better way to control it.