Dometic Duo-therm Furnace Wiring in Ceiling

[SAMe]

Hi, SAMe here again. All moved in, got fencing over roof to protect from falling branches, and now ready to tackle my one issue still remaining and that is my 2006 Puma, Dometec-Duo-therm wiring issue in ceiling to furnace.


Some weeks back I tried turning on Furnace at thermostat, and heard clicking noise over where AC unit and relay board all sit in ceiling.


Since previous owners did not use AC in ceiling cause coils/fins totally covered in dog hair and other various soot from no maintenance, I cleaned that whole area and in process of dissconnecting wires and reconnect, the clicking noised stopped occurring.


I hope to attach my wiring drawing of the ceiling stuff, but let me say, I see that there are 6 wires at thermostat, and a brown casing wire in ceiling appear encase those same 6 wires with the white one being to furnace 'F' at the thermostat.


That white wire is connected to slightly larger white wire that goes into the 'relay' board. I assume that is correct, tho maybe I made an error there.


However, there is also 2nd brown casing wire in that same AC area --not from 'relay' board-- and it has red and white wire, and the white wire is just hanging loose in ceiling. That red wire is connected to a blue/white wire that goes into relay board.


So I think that 2nd brown casing wire ---with red and white wire-- maybe go to the furnace cause I can see a brown casin wire going into the back of the furnace.


Also going into back of furnace I can see a larger purple/white bonded with a white wire, and 2nd purple/white { or dingy yellow } wire bonded with a white wire.


In ceiling 'relay' board area, I can see two purple/white wires connected together and the have red wire { +12V } --out of relay board-- connected to them. So I presume those two purple wires are from furnace.



I also see two larger white wires connected with wire nut and a black wire { -12V } out of relay board. So again, I presume those two are also from the furnace.


Now to back track. I noted there is the one loose white wire, from the 2nd brown casing wire in same ceiling AC area, but there is also a 2nd blue/white wire that is hanging loose, and it comes out of the relay board, just like the other blue/white wire does, but,
the original blue/white as I stated higher above is connected to red wire out of the 2nd brown casing wire.



Ok, so one loose white wire--2nd brain casing wire, and one loose blue/white wire out of relay board.


And finally so there is no confusion, the red wire --of six from thermostat-- is connected to a red/white wire { 7.5 + T-stat }.



So one might think the loose white and loose blue-white should go together, but since I'm not sure, I want to know if any here at FF know for sure. Ive searched forum and net trying to find wiring diagram for that whole area under AC unit in ceiling and cant find what I have.


Also the relay board has a wiring diagram on it, but it does not show what specific wires coming out of are specifically connected to.


Ok will try to attach my jpg drawing, maybe it will help Of course all of the above may just get me back to hearing the clicking noise in the ceiling and NOT actually getting the furnace to work, well that is whole other story Ive yet to get too.

[Bama Rambler]

Some pictures of the wires might help, but if the relay isn't clicking the thermostat isn't sending signal to it.

Which thermostat do you have?

The furnace supplies it's own power to the thermostat wires, so you don't need anything but a dry contact from the A/C / Thermostat for the furnace to run.

[SAMe]

Its not a digital. So I guess it is identified as 'analog'. I dunno.

Here is exact one at amason LINK

The name on it is Duo-Therm Dometic. Here is LINK with mostly pics of the analog type I have.

https://www.google.com/search?q=dome...w=1578&bih=688

As stated previously, the clicking noise I originally heard, was not in thermostat, but in ceiling near the relay board that is under AC unit on roof.

There is plastic panel inside on ceiling on all of the wires I mentioned and the relay board on behind this panel as is the flow of air that can be directed to ducting or straight into room.

Ive added a photo but it does not do the same justice as my drawing does.

On left you can see the 6 wires but not the brown casing wire they are inside of --well you can see the dark brown wire coming out of AC panel area, but then it goes out of view on left side of screen---.

You can see the lighter brown casing wire, that has the red wire and loose white wire, as I previously stated in original post.

I got the RV with most of the panel missing --as you see in the photo-- and as I stated, I cleaned this whole area, and above, and all of those wires before moving in.

They were a sooty hair ridden mess. In the process I must of either left wires dissconnected --the white from light brown casin and a blue/white from 'relay' board--- or they were already dissconnected I didnt noticed,

or possibly I reconnected something incorrectly. What I do know, is what I stated.

1} the clicking noise --from what I thought was this ceiling area did not occur upon turning switch to 'furnace' after I cleaned wires,

2} luckily the AC works fine after my cleaning. If you can read and follow my thoughts in the original post, I think I covered most everything, and,

the drawing and now a photo, should help others to get basic idea of where I am at.

Yes, I could just hook the loose white wire to the loose blue/white wire, but I dont want to make anything worse.

OH YEAH, one other thing, it is possible, that, the clicking I originally heard in ceiling was not supposed to occur at all i.e. maybe the previous owners had been in there ---obviously they had-- and they wired something incorrectly. I dunno.

I do recall, that, I thought I had finnished cleaning those wires, and I looked away and when I looked back, there was that loose white wire, so I'm liked, h,mm did I reconnec that wire but not good enough and it came loose when I looked away.

YES, I should have wrote on paper what all of the wire connections were, before I cleaned them. Long story short, I was working every day at work and burnt out for many reasons and was just in hurry cause I was on a time limit to get moved into this RV and out of the place I was in.




As for a direct line from thermostat to furnace, well I recall taking screws out of the thermostat board and seeing a brown wire, so I do believe, the white wire in thermostat connected to 'F' goes to this area under the AC unit near the 'relay' board.


Anyway I cover all of that in in original post #1. Thanks.

Originally Posted by Bama Rambler

Some pictures of the wires might help, but if the relay isn't clicking the thermostat isn't sending signal to it.

Which thermostat do you have?

The furnace supplies it's own power to the thermostat wires, so you don't need anything but a dry contact from the A/C / Thermostat for the furnace to run.

[Bama Rambler]

When you run the furnace you shouldn't hear a clicking sound from the A/C control board. If you did something was wrong.

The furnace should have a pair of wires (normally both are Blue/White) from the control board terminals T3 & T4 to the furnace. There is a triac on the board that shorts those terminals together when you connect the White wire from the thermostat to +12 volts. I suspect that the lighter brown cable is going to the furnace and the white wire from that cable is supposed to connect to the loose Blue/White wire from the control box.

You could look at the furnace to see if that cable goes there.

Here's the service manual for your A/C. On the bottom of page 37 is a wiring diagram for your unit.
Dometic A/C Service Manual

[SAMe]

Hi Bama, and thanks for getting back to me.

I had seen many of those various wiring diagrams, just not all in one document. And thanks for the Dometic PDF as it covers a lot of stuff. Thank You Thank You!

Yes, I had see on various schematics the two blu/whi wires going to furnace, but since my two blu/whi wires only extend a short distance outside of the 'relay board' in ceiling, and no sign of connection to other wires, I was perplexed as to what the next correct move would b.

Luckily, you confirmed what I was thinking made sense. This AM I lay in bed thinking, then got out and looked at what the red wire was connected to, and ---as I already knew but forgot--- it is connected to one of the blu/whi wires.

So, I just took the plunge, and connected that white wire to the other blu/wire. I got to thinking, that, since as I had thought previously, the lighter brown casing wire is coming out of furnace, it must be the one in the ceiling.

So blu/whi become red and white to furnace, not blu/whi as all of the schematics Ive seen show.

I slide themostat switch to furnace and and heard nothing ---bummer-- then I slide temperature higher and then heard clicking noise --dont know where--- but almost immediately afterwords, the fan in furnace kicked on and blowing out into my dinning room, --cause the front panel is off---.

YAY! Ha we have ignition Houston, I mean Bama-Rambler.

So next question. Do you think it matters which blu/whi the red and white connect too? If it does, then that answer may only come with some trial and error later on the pathway to actual heat.

I can see one of the circular metal side panels is off of the galvanised metal boxing of furnace around the tubes area. Not sure if that would be dangerous, if I ever get actual ignition of propane and heat.

There is bunch of dust and some debri all in that area, as well as the thin wood paneling { wall } storage area compartment.

Anyway, you've helped my greatly Bama, and my next step will to vacuum out around that side of the furnace area and see about putting the circular metal plate back on.

Until then, not sure what my next moves will be in finding out if furnace will is getting propane and ignite. Best Wishes and open to any thoughts if you have more. Today Ive got to empty black water again, then it is off to work.

Oh yeah, one other thing, after I furnace blower came on, I slide switch to off, but furnace blower fan did not shut off. So I slide temp to colder and still no shut off,

then I dissconnected one of the wires and no shut off then the other wire and no shut off, so just when I was going to look for a fuse to pull, it shut off. Probably some kind of a timer thing on furnace control board or whatever in that area.

Originally Posted by Bama Rambler

The furnace should have a pair of wires (normally both are Blue/White) from the control board terminals T3 & T4 to the furnace. There is a triac on the board that shorts those terminals together when you connect the White wire from the thermostat to +12 volts. I suspect that the lighter brown cable is going to the furnace and the white wire from that cable is supposed to connect to the loose Blue/White wire from the control box.

You could look at the furnace to see if that cable goes there.

Here's the service manual for your A/C. On the bottom of page 37 is a wiring diagram for your unit.
Dometic A/C Service Manual

[Bama Rambler]

Do you think it matters which blu/whi the red and white connect too?

No, it doesn't matter which blu/wht wire connects to red or wht. It'll work fine either way.

As for the furnace not shutting down immediately, that's normal. There's a 'cool down' timer in the circuitry that runs the blower for a certain time after the flame shuts off (when the thermostat no longer calls for heat).

[SAMe]

Ok good to know. 7,000+ post by you. What kind of engineer, if you dont mind my asking? Train? Do you have one of tose striped caps from the 30's. Kidding


I'm more familiar with the Montgomery, Dothan, Troy rt231 area. Have been on 65South to Mobile a few times, to Carnival cruise and see battleship AL.

Originally Posted by Bama Rambler

No, it doesn't matter which blu/wht wire connects to red or wht. It'll work fine either way.

As for the furnace not shutting down immediately, that's normal. There's a 'cool down' timer in the circuitry that runs the blower for a certain time after the flame shuts off (when the thermostat no longer calls for heat).

[bubbles]

[QUOTE=Bama Rambler;2369289]When you run the furnace you shouldn't hear a clicking sound from the A/C control board. If you did something was wrong.

This may not be applicable to an analog thermostat but a Dometic digital thermostat will cause a click from the a/c and if furnace mode is selected and the fan mode is not in AUTO the a/c fan will also run.

[Bama Rambler]

I'm north of Mobile, but not on the I-65 route.

Originally Posted by bubbles

This may not be applicable to an analog thermostat but a Dometic digital thermostat will cause a click from the a/c and if furnace mode is selected and the fan mode is not in AUTO the a/c fan will also run.

Years ago the control boards had actual relays on them so there was a click like the new ones with digital communications. They changed to electronic switching before the digital comm thermostats came about because it's cheaper then relays. So it is possible that there could be a click on some older analog units, but in a 2006 unit it should be electronic switching.