Air conditioner issues

[uscgcolletti]

I have a Dometic thermostat and it seems it's completely off. The thermostat does not cycle till I have it past 50 degrees. I know this is incorrect and would like to get it fixed. Where is the sensor for something like this is it in the actual thermostat or elsewhere. I'm also thinking about upgrading to a digital. Any help you can offer is greatly appreciated

[dougrainer]

Fosters wrote:
Lenr:

Well....I called Dometic directly. For my application: upgrading my dometic duo therm analog t-stat to digital, CANNOT BE DONE simply by switching out the t-stat. Which, I was hoping was not the case. Simply because look where the a/c unit is? On the ceiling in your coach! And.....the control box (an approx. 5" X 5" X 2" silver metal box) has to be replaced as well. So I need a Dometic replacement Kit: a digital white thermostat that illuminates etc. and the control box. Prices vary from Sellers from $77.44 (which I'm ordering from rvpartscountry.com) up to over $100.

A decent DIY'er, I learned from Dometic that I'm going Analog to Digital aka Single Zone. So on my current Dometic analog I have six (6) incoming lines. I'm now only using 3 and burying the other 3. As far as the control box in the a/c unit on my ceiling, until I receive the replace control box, I'm please God hoping it's a simple disconnect and replace the old wires to the new, PERIOD.

You only use 3 of the wires. BUT, the color code does not make a difference. You can use any of the 3 wires. You will have to find the Install for the Single zone Tstat/control board and determine which of the wires go to the 3 connections on the tstat. Then there are the other 2 POWER(Pos and Neg) wires already at the old control box. 12 volt, not 120 volt. WRITE down what the 3 wires go to on the wall tstat for future reference and troubleshooting. Doug

[Fosters]

Lenr:

Well....I called Dometic directly. For my application: upgrading my dometic duo therm analog t-stat to digital, CANNOT BE DONE simply by switching out the t-stat. Which, I was hoping was not the case. Simply because look where the a/c unit is? On the ceiling in your coach! And.....the control box (an approx. 5" X 5" X 2" silver metal box) has to be replaced as well. So I need a Dometic replacement Kit: a digital white thermostat that illuminates etc. and the control box. Prices vary from Sellers from $77.44 (which I'm ordering from rvpartscountry.com) up to over $100.

A decent DIY'er, I learned from Dometic that I'm going Analog to Digital aka Single Zone. So on my current Dometic analog I have six (6) incoming lines. I'm now only using 3 and burying the other 3. As far as the control box in the a/c unit on my ceiling, until I receive the replace control box, I'm please God hoping it's a simple disconnect and replace the old wires to the new, PERIOD.

[dougrainer]

lenr wrote:
Yes, I meant Dometic--bet I had a spell checker helping me out. My experience was with the Dometic 4 button digital thermostat installed OEM in a trailer built in the spring of 2013. I found the temperature control to be very imprecise meaning several degrees between turn on and turn off, which was my initial irritation. After a short while we realized that the control board actually turns the fan off for 2 seconds while switching from low to high speeds--very annoying especially in the middle of the night while sleeping. This switch up to high speed only occurs when the temperature is 5 degrees from set point which is probably feeling pretty warm. We also found that the device would not run in low speed fan continuously. In the summer of 2015 we paid our favorite AC shop to replace both the control board and thermostat which fixed the problem of not running continuously in low speed fan. However, the dead time between low and high remained, and the AC guy explained that is the way they are designed to work because a digital signal is sent from the thermostat as opposed to voltages on wires, traditionally. The dead time between speeds is a not infrequent on line complaint.

In the fall of 2015 the evaporator developed pin holes and lost the freon. Dometic gave us a replacement unit if we paid the labor. In spring of 2016 the replacement unit lost all of its freon after being used 3 out of the 8 months since installation. Our AC guy had an old unused scratch and dent unit that he had bought from Dometic on a warehouse clean out sale that we had him install for cheaper than a new one. On line there is discussion of Dometic having a lot of trouble with leaking evaporators on units made in China--we experienced 2 in a row. This last unit that we had installed was built in Elkhart, IN. Only catch about this unit was that we had to put in the 12 button remote (10 buttons in our case for single zone) and associated control board. It was almost a blessing in disguise because the 10/12 button remote and control board work great! Temperature control is very accurate and there is no dead time when switching between fan speeds.

Recommendations to last poster: If you are going to put in a Dometic digital thermostat, only use a 10/12 button single zone model--not the 4 button. Each Dometic digital thermostat has its own specific control board so you will have to change to a matching control board. However, if going from analog, I would just install a household thermostat because all the wires necessary should be available, and you don't have to change the control board in the AC unit. If you felt comfortable changing out the Dometic stuff then this would be even easier! Research house thermostats on this forum and http://www.modmyrv.com/.
Be aware that house thermostats run on 24 volts ac while RV thermostats run on 12 volts dc. So, the house thermostat just runs on the batteries that were designed for backup when the 24 volts ac is off. You may have to replace the batteries a little more often. This will be way less expensive and easier than replacing both Dometic components, and you may just like the results better.

Our favorite AC shop is National Refrigeration, Shipshewana, IN. Leon has the best price and workmanship for AC work and RV refrigerator rebuilds.

Lets fix some errors in this post.
1. You did NOT have a "4 button" tstat. You had what is called a SINGLE ZONE tstat. 4 button Dometic tstats were the original CCC that were discontinued in 2001.
2. You had to use the 12 button tstat because you obviously purchased a PENGUIN model AC which comes with the 12 button board(control package) already installed on the Penguin unit. They also had to modify the wiring to make the communication cable work for the 12 button
3. There is NOTHING wrong with the Single Zone Tstat system.
4. As to the Evap supposed problem. I work on hundreds of AC units every year and have NOT seen such a problem. I do not know where this evap problem has been reported and verified. Yes, Both RVP and Dometic units fail but I have had very few Dometic leakers. Doug

[lenr]

Yes, I meant Dometic--bet I had a spell checker helping me out. My experience was with the Dometic 4 button digital thermostat installed OEM in a trailer built in the spring of 2013. I found the temperature control to be very imprecise meaning several degrees between turn on and turn off, which was my initial irritation. After a short while we realized that the control board actually turns the fan off for 2 seconds while switching from low to high speeds--very annoying especially in the middle of the night while sleeping. This switch up to high speed only occurs when the temperature is 5 degrees from set point which is probably feeling pretty warm. We also found that the device would not run in low speed fan continuously. In the summer of 2015 we paid our favorite AC shop to replace both the control board and thermostat which fixed the problem of not running continuously in low speed fan. However, the dead time between low and high remained, and the AC guy explained that is the way they are designed to work because a digital signal is sent from the thermostat as opposed to voltages on wires, traditionally. The dead time between speeds is a not infrequent on line complaint.

In the fall of 2015 the evaporator developed pin holes and lost the freon. Dometic gave us a replacement unit if we paid the labor. In spring of 2016 the replacement unit lost all of its freon after being used 3 out of the 8 months since installation. Our AC guy had an old unused scratch and dent unit that he had bought from Dometic on a warehouse clean out sale that we had him install for cheaper than a new one. On line there is discussion of Dometic having a lot of trouble with leaking evaporators on units made in China--we experienced 2 in a row. This last unit that we had installed was built in Elkhart, IN. Only catch about this unit was that we had to put in the 12 button remote (10 buttons in our case for single zone) and associated control board. It was almost a blessing in disguise because the 10/12 button remote and control board work great! Temperature control is very accurate and there is no dead time when switching between fan speeds.

Recommendations to last poster: If you are going to put in a Dometic digital thermostat, only use a 10/12 button single zone model--not the 4 button. Each Dometic digital thermostat has its own specific control board so you will have to change to a matching control board. However, if going from analog, I would just install a household thermostat because all the wires necessary should be available, and you don't have to change the control board in the AC unit. If you felt comfortable changing out the Dometic stuff then this would be even easier! Research house thermostats on this forum and http://www.modmyrv.com/.
Be aware that house thermostats run on 24 volts ac while RV thermostats run on 12 volts dc. So, the house thermostat just runs on the batteries that were designed for backup when the 24 volts ac is off. You may have to replace the batteries a little more often. This will be way less expensive and easier than replacing both Dometic components, and you may just like the results better.

Our favorite AC shop is National Refrigeration, Shipshewana, IN. Leon has the best price and workmanship for AC work and RV refrigerator rebuilds.

[Fosters]

lenr wrote:
Sounds like you have an analog or mechanical thermostat. You could upgrade that to a home style digital. Google for or check mod my rv. To use the Domestic digital you would have to upgrade the control box. The Dometic thermostat works fine for some and terrible for others having inconsistent temp control which was one of my problems with it. Don't suggest Domestic digital for an upgrade.

You mean "Dometic" correct?

I'm preparing to purchase the Dometic digital upgrade kit, which includes a dometic brand of course digital t-stat and a dometic control box. My current a/c & furnace works just fine with the analog. I just want digital for a better reading and more concise temp setting that I want. Please tell me why you are against the Dometic upgrade? Thx!

[uscgcolletti]

Ok update:
Changed filter, wasn't needed but I done it anyway.
I've also took compressed air and blew the Tstat out. Seems slightly better but not like I remember it.
Quick question... can the Tstat just be changed with a digital or does the sending unit needs to be replaced aswell?
I was at Ace and saw a generic Digital and seemed pretty easy to install.

[Gene_Ginny]

deleted - wrong info

[uscgcolletti]

I'll try that today when I get home.

[dougrainer]

uscgcolletti wrote:
So the sensor is on the main unit and not the tstat?

The sensor IS the wall tstat. Try cleaning out the tstat board with PC compressed air. There may be dirt build up causing the sensor to not read correctly. Doug

[uscgcolletti]

I never said anything about heat or furnace

[MrWizard]

assuming you want to heat to cut off below 50 degrees

what makes you think the T-stat is faulty

what is the RV inside temp, 50, 60 , 49 ?

the heat is not going to come on until the stat is set above room temp

is the RV only 30-40 degrees and you want 45 degrees ?

you have not given enough info

heat pump or LP furnace

[uscgcolletti]

So the sensor is on the main unit and not the tstat?

[time2roll]

> Dometic digital thermostat

[lenr]

Sounds like you have an analog or mechanical thermostat. You could upgrade that to a home style digital. Google for or check mod my rv. To use the Domestic digital you would have to upgrade the control box. The Dometic thermostat works fine for some and terrible for others having inconsistent temp control which was one of my problems with it. Don't suggest Domestic digital for an upgrade.