dometic thermo prob

[aurcor]

Hello, new to RV life and this forum.

Recently my wife complains that our thermostat doesn't shut off properly. It did keep the heat on one time until we were cooking (way above set temp). [ dometic duo therm comfort control center with phone plug connection]

I finally bought an inexpensive replacement on Amazon. [White Rodgers 1C20-101 Economy 24 Volt/Millivolt Heat Thermostat] And thought it should work for our heating/cooling needs.

Last night I traded it out by cutting the wire with the RJ-8(ish) plug and connected the wires to the new thermostat, following the chart provided by new thermo mfg.

It did not work.

So I re-connected the phone plug to the original cable and inserted back into our Dometic CCC thermostat, and nothing. No backlight screen or anything.

Note: while I was trying to connect the new analog thermo the Red and Green wires touched long enough to smolder and melt some insulation.

I'm willing to take common 'you did what?'s' in replies in my ignorance, but don't forget to provide a possible solution.
thanks in advance

[time2roll]

WOW! What a great success story 🙂

[aurcor]

UPDATE -
I went ahead an purchased the upgrade kit from Dyers RV online. (we got the 5th wheel for one dollar, and we are going to keep it, so it was worth it)

Just got Back from Montana, and it was in the mail. So I put it in today. I had EE error code on the thermo, once I reconnected electrical. I did a 5 button CCC reset and it worked. However, only one mode showed, so I had to turn the furnace DIP switch to ON and performed another reset.

We are working again! thanks for all your suggestions. and assistance!!

[aurcor]

I guess I will use the existing cable if it may be too difficult to install a new one.

It should be ez to reconnect the plug I cut off to the wire hanging out of the wall... following the colors on the cable. (matching each color, assuming the other end is reversed)

[dougrainer]

aurcor wrote:
thanks again!

We are keeping the RV so I will get the upgrade kit. (Thanks Doug)

Instead of reconnecting the jack on the TSTAT side.
would this work?
https://www.dyersonline.com/dometic-a-c-18ft-communication-cable.html

Also, what change came with 5 button? just zones?

Regs,

cj

HOW are you going to run that COM cable from the roof AC to the wall tstat easily? Just remember, the difference between a COM phone type cable and a Phone cable is the wires are reversed at the end. LOOK at a standard phone cable and how the 4 wires are installed in the modular end. Then look at your AC cable. Just reverse the end you cut from the AC end and install a new 4 wire modular cable end. OR, unless you threw the end you cut off away, just look at how the wires are situated and install a new end just like the cut off piece. Doug

Look at Page 9 of this link

https://www.intechtrailers.com/images/info/PDF/Dometic/schematics-ac-diagrams.pdf

[dougrainer]

aurcor wrote:
thanks again!

We are keeping the RV so I will get the upgrade kit. (Thanks Doug)

Instead of reconnecting the jack on the TSTAT side.
would this work?
https://www.dyersonline.com/dometic-a-c-18ft-communication-cable.html

Also, what change came with 5 button? just zones?

Regs,

cj

The change was 2 things.
1. To change ZONES(having more than 1 roof AC unit) required you to push 2 buttons at the same time and people either did not know that or forgot and had a problem controlling multiple AC units
2. The 4 button could not have a FREEZE control for Heat Pumps. The 5 button(which does have a Zone button which is the 5th button) has a Freeze Thermister which will work in hot and cold evap temps.
3. When you buy the new kit, you will remove the existing BiMetal freeze control and install the included Freeze Thermister in its place. The 4 button freeze control will not work with the 5 button circuit board. Doug

[aurcor]

thanks again!

We are keeping the RV so I will get the upgrade kit. (Thanks Doug)

Instead of reconnecting the jack on the TSTAT side.
would this work?
https://www.dyersonline.com/dometic-a-c-18ft-communication-cable.html

Also, what change came with 5 button? just zones?

Regs,

cj

[dougrainer]

aurcor wrote:
thanks all.

it is a 97 Mobile Scout 33RK We don't really use the AC but am going to need to get heat going asap. Overnight temps already dipping to low 30's.

There is only one AC. I did check the only fuse I could see in the heater compartment, and it was not blown. I found some CcC units on Amazon (4 to 5 button) If those will work i will purchase one of those.

First I would like to check the sensors (?) and see if I can't get the backlight going again on the old one. and I can re-terminate the cable with the plug so there is no funky splicing.

I will let you know how it goes.

CJ

If you plan on keeping the RV, I would NOT buy a 4 button from any vendor. The 4 buttons were discontinued in 2002 and stock disappeared about 2005. So, it would be a stretch to find a NEW 4 button which is what you have. Rebuilt 4 buttons are probably what they are selling. Your best bet is to but a 5 button kit and install. This is the upper control board in the AC and the 5 button wall tstat. This is a link to just 1 vendor but this is the kit I would get for my unit. Doug

PS, that silver box is where the fuse(3 amp) is located. Also, you do NOT have a remote sensor. The 4 button is the sensor.

https://www.dyersonline.com/dometic-air-conditioner-5-button-comfort-control-center-upgrade-kit.html...

[A1RVTraveler]

cavie wrote:
Me thinks you need an RV tech to repair this. Your knowledge is lacking as you are in this position.

This is the best solution. The fuse is in the upper unit on the circuit board near the capacitors.

[robatthelake]

there is a work around using just the Furnace wiring and an everyday coil type of Thermostat!
It takes a bit of effort and a schematic to see which wires to splice into.
I can say that the Telco Wire is not used to perform this !
I just followed the installation instructions that are available on line for the furnace itself ,mine is a Suburban!
A Thermostat is just a Switch that opens and closes automatically to a set temperature!

[shepfly]

I'm pretty sure that fuse Doug mentioned is in the control box with you capacitors in the rooftop unit under the outer cover and inside the electrical box. I don't believe you can switch to a five button thermo without also changing the upper control board to match the 5 button thermo. Also the phone style control cable is NOT a phone cable, the ends are REVERSED, so be sure to duplicate the cut off end when you reattach the plug. Good luck, Dave

[aurcor]

thanks all.

it is a 97 Mobile Scout 33RK We don't really use the AC but am going to need to get heat going asap. Overnight temps already dipping to low 30's.

There is only one AC. I did check the only fuse I could see in the heater compartment, and it was not blown. I found some CcC units on Amazon (4 to 5 button) If those will work i will purchase one of those.

First I would like to check the sensors (?) and see if I can't get the backlight going again on the old one. and I can re-terminate the cable with the plug so there is no funky splicing.

I will let you know how it goes.

CJ

[cavie]

Me thinks you need an RV tech to repair this. Your knowledge is lacking as you are in this position.

[dougrainer]

1. YOU DID WHAT:B
2. You cannot install a normal Tstat in place of the Dometic CCC system.
3. Those wires you cut are NOT regular tstat wiring. They are a 4 wire communication cable. The Tstat end plugs into the wall tstat. The other end will plug into the roof AC control board.
4. You MUST use a Dometic wall tstat. If you have a 4 button Doimetic you have to replace with a 4 button. BUT the 4 button was discontinued almost 18 years ago and no new ones available. The 5 button replaced the 4 button and IS available. The newest is the 10 button which is NOT compatible with your older control board unless your unit is newer than 5 years ago and may have the 10 button.
5. Odds are when you cut the cable end off you blew the 3 amp fuse on the upper AC control board. That is why you have no display when you spliced the wires back.
5. Now, since you did not state year/Model/Brand of RV and how many AC units, the wall tstat may NOT be the temp sensor. The Dometic system has the option of remote sensors and IF there is a remote sensor connected to the upper AC control board, the wall tstat will not be the temp sensor. Doug

[Matt_Colie]

Aurcor,

If you cut through the "RJ" cable with a single cut, it is almost certain that you blew a fuse back in the unit.

Matt