My home is wired for the thermostats with two wires (red and white). I have acquired a new thermostat that requires a Red, White, and Common wire. Using the white wire in that position will power the unit up but it won't trigger the heat. Is there something that can be put in line that will allow this thermostat to work without rewiring the house?
Connect a new piece of 3 wire to the existing 2 wire and pull it through the wall by pulling the 2 wire. Of course if it gets stuck you will need to measure how far you pulled to know where to cut a hole in the wall. Cutting a hole in the wall if needed, isn't a big deal you just put the piece back, screw or nail it down (cut so you have studs on both sides to reattach it later) tape and plaster and paint.
T-stat wires are usually left loose in the wall, no staples, so you can easily replace it by pulling a new wire through with the old one. First try to get an idea of where the wire goes. Get an estimate of total length and go to home depot and purchase 18-3 t-stat wire. They sell it in 25 feet, 50 feet, 100 feet, 500 feet, or by the foot. Compare prices and get enough to make a continuous run. Older 2 wire Tstats used a mercury or spring switch to simply connect the two wires together (24v + and sl return). Your new Tstat needs a common because it is being powered by the same feed that activates the unit. (So you have 24+ 24- and sl return) When you attach your new wire to your old wire be sure to actually strip the outer coating of about 4 inches or so and fold the wires around each other to get a good strong bond, and then tape it tight to keep it as small diameter as possible.
2 wire is milivoltjust scrap off varnish off wires and try again dc voltage produces varnish on wires prevents heater from firing
