750mv vs 12v Thermostat Question UPDATE 2
Updated 29 Nov-- Update 2--29 Nov: got it to work. Not clear on the thermostat voltage for these things whether I can use the cheaper version or what. I want it for my furnace only set-up in the R...
Forum Discussion
BFL13 wrote:
Well this is embarrassing---The two wires into the back of the old thermostat are both blue! I was all wrong about pos and neg.
EDIT--- OR NOT ???
I put the meter across the old one's two blue wires at W and R common and got 13.85 volts. Switched leads and got -13.85 volts. The positive reading was with the pos lead on Terminal R common in the manual's diagram and the neg (common as marked on the meter) on W
Seems backwards? Anyway now I am sort of nervous which wire to put where on the new thermostat.
The wiring diagram on page 5 in that link does show the two blue wires to the thermostat as "Thermo + " and "Thermo" but not where they go in the thermostat.
My manual's diagram says "connect the two wires which run from the furnace to the back of the thermostat base" Doesn't say which terminals for which wire.
here is a test you can do. worst case it will blow the fuse for the furnace, but I seriously doubt it.
u
take the two wires going to the furnace. touch them together. If the furnace starts to run, which i suspect it will, connect one wire to the W and one wire to the R on the thermostat.
If the fuse blows, then you haven't found the correct wires going to the furnace. I doubt that is what will happen based on your description.
