Removed rooftop ac but want heater still

[cbaggese]

Hi all,

This is my first post on this forum.

So, I removed the rooftop ac to replace the roof and left it off because I have no shore power anyway. But that seems to have caused the heater to not work. A tech rewired the controller(?) box to "complete the circuit" but the heater is still not working.

I can't use the ac so putting it back doesn't make sense to me. Is there another possible issue? Is there any other solution? Any helpful responses would be great. Thanks!

 

[Domo]

Year, make and model of your RV would help us to help you.

Hope you didn't pay the tech if he/she did not solve your issue.

 

[edjunior]

First, welcome to the forum. Now, for when the experts come along, please let us know what kind of RV you have. Also what kind of AC you have (had). Also, more out of curiosity, why do you not have shore power? Do you go camping where shore power is available, or is it all "dry" camping? Just wanting to know more about your situation. Again, welcome to the forum, and hope to see you down the road!

 

[NY_Dutch]

I think the important piece of information is the brand and model of your furnace. The answer may be as simple as replacing the thermostat with a basic heat only model that typically only needs a two wire connection to the furnace.

 

[Gary RV_Wizard]

What NY Dutch said. Your thermostat needs two things to control the furnace:

1. A source of 12v power
2. A wire to the furnace to signal heat demand.

In a system where there is both a/c and furnace, typically the thermostat gets its 12v power from the a/c controller board and and sends its heat/cool demand signal back to the same board. When heat is needed, the signal gets forwarded to the furnace heat demand wire terminal. That obviously can't happen after you removed the a/c. I presume your tech attempted to connect the remaining wires as a substitute but that didn't work.
The simpler solution might be to install a new heat-only thermostat but that involves running a pair of wires to the furnace, one to get 12v power and the other to signal heat demand. Whether that is easy or impossible depends on the furnace & thermostat locations and how your RV is laid out.

 

[John From Detroit]

Honeywell Heating Dial Non-Programmable Thermostat - Ace Hardware

The Honeywell CT30A1005 Heat Only Thermostat has low voltage controls with a snap-action switch for heating systems. This non-programmable thermostat comes with mounting hardware (wall plate included) and does not require leveling. For straightforward temperature control, there's no substitute...

www.acehardware.com

Or any of the others you find like it
The one I got from ACE was a house brand. Pure mechanical. NOT a mercury filled bulb (I do not think they make those any more) So need not be level.. Just two screw type connectors and I spliced into the leads that ran from the Furnace to the Carrier AC (Where the controls were) Taped off the leads at the AC when we replaced it. Worked way better too I might add.Oh.. I did add a toggle switch in series with it so I could LOCK OFF.

 

[Ray-IN]

All you need is this $9 thermostat and omit the cooling wires. Amazon.com
Or if you want something very basic-looking that is heat only, this one is $17: Amazon.com

 

[Lou Schneider]

Some Dometic thermostats send serial data to a control box inside the air conditioner plenum, which decodes it and decides whether to activate the air conditioner or the furnace. The furnace control is just an on/off contact but it comes from the ceiling box, not the thermostat.

If you can't make the furnace work by shorting a couple of wires going to the thermostat it may be one of these and you'll have to run a new pair of wires directly from the furnace to the new thermostat.

 

[Kirk]

If you get a basic thermostat that is only for the furnace like this one, it only needs to be wired to the 2 blue thermostat wires of the furnace. It then connects when heat is needed and opens when set temperature is reached. Very simple and reliable.

 

[cbaggese]

Hi all,

My RV is a 2002 Aljo Scout by Skyline. I did pay the tech already. I don't have shore power because I am boondocking in my RV on my property while I plan to build my house. I did have the tech reconnect the wires, because the heater was working when only the part of the ac that sits on top was removed but the "controller box" was in place. Only after removing the box did the heater stop working. I do prefer to use the existing wiring if at all possible. I've attached photos for reference.

Thank you for your help.

 

[TheBar]

Make sure your 12 volt batteries are charged and connected.

 

[Ray-IN]

In the picture of the wiring diagram, top right of the schematic shows 2 blue/white wires to furnace. The actual furnace 'stat wires might be red and black, you'll see when you trace the blue/white wires. That's the wires you need to attach to one of the simple bi-metal 'stats recommended. The digital probably require a battery, you'd have to read the 'stat specs.

 

[Lou Schneider]

Hi all,

My RV is a 2002 Aljo Scout by Skyline. I did pay the tech already. I don't have shore power because I am boondocking in my RV on my property while I plan to build my house. I did have the tech reconnect the wires, because the heater was working when only the part of the ac that sits on top was removed but the "controller box" was in place. Only after removing the box did the heater stop working. I do prefer to use the existing wiring if at all possible. I've attached photos for reference.

Thank you for your help.

Your system is as I described earlier - the thermostat communicates with the controller box which then controls whether the air conditioner or furnace starts. There is no direct connection between the thermostat and the furnace.

You'll have to replace your existing thermostat with one that can control the furnace directly via a contact closure. Then you'll need a two wire connection directly from the thermostat to the furnace.

The cleanest and most direct way to do this would be to run a new wire directly from the new thermostat to the furnace eliminating the wires going up and back from the ceiling.

If you want to use the "existing wiring" you'll have to choose a pair of wires going from the new thermostat to the controller box location and splice them to the two wires going from the controller box to the furnace. These are labeled "blue/white" in the schematic of the controller box but likely are different colors outside of the box. The wires going to the furnace will be connected to the pins in the plug that mate to those pins in the socket.

If you decide to make a splice in the ceiling you'll have to leave a way to get to it in case it develops a problem in the future.

 

[OldWEB]

Just to see if the furnace circuit is functional, tie the two blue/white wires together where the controller was. Furnace should turn on, if so, then you could mount a thermostat at the ceiling... nothing fancy.

 

[Kirk]

You'll have to replace your existing thermostat with one that can control the furnace directly via a contact closure. Then you'll need a two wire connection directly from the thermostat to the furnace.

a basic thermostat that is only for the furnace like this one,

There are two wires from the furnace that currently go to the air conditioner control circuit board. To use them you will need to figure out which ones they are. If you share what furnace you have we can give you specific instructions on how to find them at the furnace.

 

[NY_Dutch]

a basic thermostat that is only for the furnace like this one,

There are two wires from the furnace that currently go to the air conditioner control circuit board. To use them you will need to figure out which ones they are. If you share what furnace you have we can give you specific instructions on how to find them at the furnace.

It's in the photos he posted. He has an Atwood 8525-IV-DCLP. The two blue wires from the four wire plug at the furnace ignitor board are the thermostat as you know, and hopefully the installer maintained the color coding up to the A/C control board.