Dometic Thermostat accuracy?

I stuck a "real" thermometer on the wall next to the thermostat. The Dometic thermostat has never been even close. And there does not appear to be any type of adjustment.

I have the same dual zone, 5 button Dometic Tstat but AquaHot instead of propane furnace plus a third zone on it's own Tstat and senor in the bathroom. During the day I adjust them much the same as at home... 74 in the summer and 68 during the winter. I just used my IR temp gun to compare the difference in indicated temp and actual. It's 1 degree warmer than the set temp of 74 and have never felt the need to check the difference before so I do not have your problem and do not know if it can be adjusted.

I would send a PM to DougRainer as he knows these systems very well as a RV teck. He will know and willing shares his knowledge.

If the sensors are mounted on an exterior wall, they may be impacted by the outside temps as the RV walls are not super as far as insulative properties.
On our coach, the one for the front zone was mounted on an exterior wall and would run the AC too much on hot days and run the heat too much on cold days. I relocated the sensor on a 2" long dowel to get it away from the wall and it now works much better.

The accuracy of your system is 5 degrees Plus or Minus per Dometic. There is NO adjustment anybody can make. The problem is the OEM. They mount the remote sensors in places that do not reflect true accurate temps. Another problem is when you have Roof Heat Pumps. The system must be installed where the Hot/Cold air coming down from the roof can sense the cabin temp and also the Hot air from the furnace that comes from the bottom up to sense the cabin air temp. They try to get a medium, but usually fail. The temp sensors are just small bulbs on a wire. Remove the sensor cover and remove the plastic wire clamp if Monaco installed it. Hang the probe outside the cover and see if it is more accurate. That plastic wire clamp if pushing on the temp sensor end can cause false readings. Do NOT install that plastic wire loom clamp, but make sure you do bot allow the temp probe to fall into the wall. Monaco used to install the front remote sensor by the front overhead CRT TV and by the back side of the drivers chair overhead compartment. Both of those locations were "Hot" areas due to the TV and the front windshield and caused temp control problems. Monaco allowed us to relocate under warranty if that was the case. You can also buy 2 new remote sensors and install them in the roof a few feet from the AC control area. You run the wire down the overhead duct and then out and mount on the ceiling between the exhaust grills. Both Tiffin and Fleetwood mount theirs in this location. Doug

JimM68 wrote:
Our Monaco has the 5 button Dometic thermostat, controlling 2 atwood furnaces and 2 dometic penguin a/c's with heat pumps.
It has remote temperature sensors, 1 near the passenger seat, and 1 on the sidewall near the back of the bedroom.

the systems have worked perfectly, except the digital thermostat settings have never been close to "Real" particularly with the furnaces.

Our "comfortable" night furnace setting is 53 degrees!
First thing in the morning, I'll bump em up to maybe 58-61...
The actual temp in the coach at night is cool but not chilly, and it is warm during the day set to 60.

The front/rear zone behavior is identical. (Thinking this would rule out a sensor or sensor location problem)

The a/c's / heat pumps are similar, but not as bad, it is the propane furnaces that are "way off"

Is there any kind of adjustment / setting so these things more accurately reflect "Reality"?

the sensors will not change their reading no matter furnace or AC.
so if it reads 60 on ac it will read 60 on furnace.
like other have suggested tape a thermostat where the sensors and see what they read before doing anything
the one on the rear wall is really not placed correctly most remote sensors are in the ceiling one frontal area and one bedroom area
After reading where your sensors are located you would have to set your stats a good 10 degrees cooler or warmer to have the wanted temps in the middle of the motorhome
to me the sensors are way too far forward and too far back

from modmyrv.com: The standard analog thermostat found in most RVs doesn’t control the A/C and furnace with much accuracy. The “set” temperature is not always the temperature the thermostat cycles, which results in as much as a +/- 5°F temperature change before the A/C or furnace cycles on or off. This is known as the hysteresis of the thermostat. For example, if you have the furnace set at 72°F, this could mean the temperature would fall to 67°F before cycling on and rise to 77°F before cycling off! These temperature swings aren’t very comfortable so what to do? The digital thermostat mod of course. Analog thermostats have what’s called a mechanical heat anticipator, which essentially tells the thermostat when to cycle. Some anticipators are more accurate than others but for the most part are not very good at controlling temperatures accurately. The digital thermostat is much better at temperature control since it controls its hysteresis using electronics to within +/- 1°F degree of accuracy.

This mod is commonly performed using the Hunter brand residential thermostat. It’s cheap and very straightforward to install. Other residential thermostats can be used but this one seems to be the most popular. Just be sure the thermostat you select is battery powered.
We have not done this modification, we just got used to the fact that there are variances in the temperature and set the thermostat accordingly.

sdianel wrote:
from modmyrv.com: The standard analog thermostat found in most RVs doesn’t control the A/C and furnace with much accuracy. The “set” temperature is not always the temperature the thermostat cycles, which results in as much as a +/- 5°F temperature change before the A/C or furnace cycles on or off. This is known as the hysteresis of the thermostat. For example, if you have the furnace set at 72°F, this could mean the temperature would fall to 67°F before cycling on and rise to 77°F before cycling off! These temperature swings aren’t very comfortable so what to do? The digital thermostat mod of course. Analog thermostats have what’s called a mechanical heat anticipator, which essentially tells the thermostat when to cycle. Some anticipators are more accurate than others but for the most part are not very good at controlling temperatures accurately. The digital thermostat is much better at temperature control since it controls its hysteresis using electronics to within +/- 1°F degree of accuracy.

This mod is commonly performed using the Hunter brand residential thermostat. It’s cheap and very straightforward to install. Other residential thermostats can be used but this one seems to be the most popular. Just be sure the thermostat you select is battery powered.
We have not done this modification, we just got used to the fact that there are variances in the temperature and set the thermostat accordingly.

not sure what your point is but the OP already has a digital 5 program thermostat with remote sensors

Very first thing I did on both coaches we've owned is swap the thermostats for reliable digital ones. This is another thing on a long list of things that makes me wonder why manufacturers don't spend the extra $10 to install a decent thermostat. I would gladly pay the cost and then some to have it come that way. It's such a small price to pay with a huge benefit. They are not only more user friendly, offer better comfort and customer appreciation but more eco friendly as well. Instead they knowingly slap in junk to save what literally amounts to only a few dollars. The funny thing is, it doesn't seem to matter how much you spend on your coach. I've seen the same thermostat that came in my entry level on a $300k coach. Guess you have to buy a Prevost to get a decent thermostat.

donfrump wrote:

sdianel wrote:
from modmyrv.com: The standard analog thermostat found in most RVs doesn’t control the A/C and furnace with much accuracy. The “set” temperature is not always the temperature the thermostat cycles, which results in as much as a +/- 5°F temperature change before the A/C or furnace cycles on or off. This is known as the hysteresis of the thermostat. For example, if you have the furnace set at 72°F, this could mean the temperature would fall to 67°F before cycling on and rise to 77°F before cycling off! These temperature swings aren’t very comfortable so what to do? The digital thermostat mod of course. Analog thermostats have what’s called a mechanical heat anticipator, which essentially tells the thermostat when to cycle. Some anticipators are more accurate than others but for the most part are not very good at controlling temperatures accurately. The digital thermostat is much better at temperature control since it controls its hysteresis using electronics to within +/- 1°F degree of accuracy.

This mod is commonly performed using the Hunter brand residential thermostat. It’s cheap and very straightforward to install. Other residential thermostats can be used but this one seems to be the most popular. Just be sure the thermostat you select is battery powered.
We have not done this modification, we just got used to the fact that there are variances in the temperature and set the thermostat accordingly.

not sure what your point is but the OP already has a digital 5 program thermostat with remote sensors

The point is that the dometic or coleman mach stats that come with the units are junk. The only way to get a reliable one is to install your own.

Effy wrote:

donfrump wrote:

sdianel wrote:
from modmyrv.com: The standard analog thermostat found in most RVs doesn’t control the A/C and furnace with much accuracy. The “set” temperature is not always the temperature the thermostat cycles, which results in as much as a +/- 5°F temperature change before the A/C or furnace cycles on or off. This is known as the hysteresis of the thermostat. For example, if you have the furnace set at 72°F, this could mean the temperature would fall to 67°F before cycling on and rise to 77°F before cycling off! These temperature swings aren’t very comfortable so what to do? The digital thermostat mod of course. Analog thermostats have what’s called a mechanical heat anticipator, which essentially tells the thermostat when to cycle. Some anticipators are more accurate than others but for the most part are not very good at controlling temperatures accurately. The digital thermostat is much better at temperature control since it controls its hysteresis using electronics to within +/- 1°F degree of accuracy.

This mod is commonly performed using the Hunter brand residential thermostat. It’s cheap and very straightforward to install. Other residential thermostats can be used but this one seems to be the most popular. Just be sure the thermostat you select is battery powered.
We have not done this modification, we just got used to the fact that there are variances in the temperature and set the thermostat accordingly.

not sure what your point is but the OP already has a digital 5 program thermostat with remote sensors

The point is that the dometic or coleman mach stats that come with the units are junk. The only way to get a reliable one is to install your own.

But you missed my point also.their post talks about analogue stats ?? the OP has a digital that's why iam not sure why they brought up the article on the analogue stat. ???
mine is a Rv Comfort.ZC(coleman) digital with remote sensors and very accurate
one sensor in the middle of the ceiling in the front living/kitchen area and one in the middle of the bedroom area