Thermostat Inop After Disconnecting Furnace

Thank you all for the insight. At the old furnace connector, I spliced the 12V supply wire to the thermostat 12V wire. The thermostat now powers up and the air conditioner runs.

CJW8 wrote:
You could also upgrade to a Hunter or other thermostat that is self powered by it's own battery.

You still need power to operate the relays in the roof unit.

You could also upgrade to a Hunter or other thermostat that is self powered by it's own battery.

atp20 wrote:
Hello,

After removing my Suburban furnace, the RVComfortHP thermostat does not energize. This means the A/C does not work.

The wiring plug to the furnace is now disconnected. Perhaps the thermostat needs those connections.

How can I restore the thermostat to operation? Must the furnace cable be jumpered?

Thank you,
Jerry S.
2003 Leisure Travel Spirit
South Florida

every application I've seen powers the thermostat from the furnace, it's probably the easiest to wire. You should be able to jumper the 12V and ground wires for the thermostat into the furnace 12v and ground feeds.

Try this... Get a small 12 volt lamp and socket.. I'd recommend a License Plate Lamp socket from the HELP panel at your local auto parts store and a Dash Indicator size lamp.

The blue wire to the "T-Stat" from the furnace (There are two) try hooking one lead of the socket to the blue, and the other to 12 volt positive.

If T-stat now works.. Good. If not.. Try other blue wire. Tape off blue wire you don't use.

Your thermostat needs 12V to operate. Was the 12V lead coming from the furnace? If so, you can jumper it for a temporary fix - or just put the furnace back in.

Yes. The roof AC tstat sometimes gets its 12 volt power from the connected furnace. You have a 12 volt positive input to the furnace and you then have 0ne of the BLUE tstat wires from the Furnace that is HOT (12 volts) that goes to the wall tstat and THAT wire supplies power to the Wall tstat and roof AC system. You have 2 blue wires. jump the 12 volt to one of the blue and see if you have power. If not, jump the other blue wire. Do NOT have BOTH blue wires connected. Doug