dometic thermo prob

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

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

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

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

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

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!

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.

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?utm_medium=shoppingengine&utm_source=googlebase&gclid=EAIaIQobChMI-sK5zIG15QIVgSCtBh0IAASeEAQYBCABEgI8h_D_BwE

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

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