Blue Wires on Furnace Question and how wired to Thermostat?

[Skyliner]

Hi,
Had to pull my furnace today to take care of a mouse problem and install a screen in the duct outlet to prevent critters from nesting in my ductwork.

Anyway, I decided to extend the wiring to the furnace (12 volt red and 12 v ground) and 2 blue wires with quick disconnects so I can pull the furnace quickly and easily next time I need to do some work on it.

Anyway, I'm not sure which blue wires goes where? I know that the blues are for thermostat control but does it matter which one is attached to the thermostat leads in the furnace bay?

Can I damage something if I install the wrong blue wire to the 2 wires headed back to to thermostat? I see one post on the Duetherm thermostat that says furnace, where does the other blue wire go?

PLEASE HELP

Please help. I don't want to screw anything up. I spent 8 hours cleaning the ducts out today. You won't believe how much mouse crap, nest material, acorns, I was able to remove today.

I used a mixture of Odoban and bleach to clean the ducts and also used the same mixture to wipe down the exterior of the heat exchanger that warms the forced air.

[Skyliner]

27 views and no reply?

I did some research and found that one of the blue whites is + . So I'm assuming that this blue wire is attached to the wire that goes to the furance post on the thermostat? Where does the other blue wire connect to? Please don't laugh but I'm color blind in reds/greens so this is a little difficult for me.

[VinceU]

Check for a wiring diagram under Suburban, I've seen them there. Are the leads blue or one w/stripe. Could be the circuit is polarity sensitive.

[clr]

OK I looked at my Atwood furnace wiring diagram and I think the following is correct but no grantees. The thermostat is a open close type of switch in this case. So I do not think that you can mess something up if you connect it wrong since both blue wires only connect to the single switch in the thermostat one side in and the other is out.
Hope this helps you out.

[Bama Rambler]

You may get more response if you told us which furnace you have.

Looking at the service manuals, all the thermostat does is close the circuit between the blue wires, so it doesn't matter which goes where.

It would have been nice if you had marked them, but it doesn't look like it matters.

Edit: I was slower than clr, but we both found the same thing.

[Skyliner]

Oops, I figured all FR products used Suburban furnaces. Its 30k BTU based on literature....schematic diagrams and labels are badly faded and impossible to read.

[Bama Rambler]

It looks like both Atwood and Suburban handle the blue wires the same.

[AlmostGood]

My RV has a Suburban furnace with 2 blue wires and old analog thermostat,
One blue went to the (R)red and the other blue wire went to the (W)white of my old thermostat.

I know the old thermostat handle the blue wires like switch, open/close.

But with my new digital thermostat the manual said connect the (W)white wire to the furnace and the (R)red to +12vdc.

So do I just connect one of the blue wires to the (W)white wire on the thermostat, which doesn't make sense?

Or do I need to add a relay or something.

Any help would be appreciated.

[Bama Rambler]

Which digital thermostat do you have?

It shouldn't make a difference which you connect to which. It should just be pulling in a relay and they don't usually care about polarity. If it doesn't work one way, swap them.

[AlmostGood]

Originally Posted by Bama Rambler

Which digital thermostat do you have?

It shouldn't make a difference which you connect to which. It should just be pulling in a relay and they don't usually care about polarity. If it doesn't work one way, swap them.

It's a Coleman 83303362 Thermostat