So, being the solutions sort of person I am, I ventured forth to get a programmable thermostat. Nothing fancy, just something that would let me set a cooler temprature at night and heat the place up when I got home. I went with the good old Honeywell junk, because apparently that’s all home depot sells (shutter, I have to stop going there…) They had three models with no price ( I lied, one did have a price), one looked too fancy, so I ignored it. The last two seemed identical, but one had a blue illuminator. I take both options, vowing to buy the cheaper of the two, even if that ment a life with no blue light on my thermostat. Turns out that the blue light model was $10 cheaper, so my life is atlast fulfilled!

I get home and liberate the thermostat from it’s plastic clam shell, only to find the instructions to be useless. See, They’e all about colors of wires, except not. They want you to use your old thermostat to figure out what wire does what. The problem with this is that two wire manual thermostats don’t care what wire is what; but, digital ones do. I figured I had a 50/50 chance that I would guess wrong. I traced the wires from the source to the wall and really, there was no indication of what color could be what. Black isn’t a normal HVAC color, and red is apparently not used in preference for more flashy colors. Basically, who ever installed this, didn’t follow any standard setout at all… Of course, after careful reading, it appears that the industry standard is the mix the colors up as much as possible to ensure you have repeat business replacing thermostats.

So I did something incredibly clever. I calculated that I could run a single blue LED off the 24VDC wire with a 1.2Kohm resistor. With the clever application of a diode, I could prevent myself from hooking it up with the wrong polarity and damaging the LED. I just twisted and taped this all together (I would of taken a picture, but I took it appart right away…) At any rate, it was a simple as hooking the wires up to either lead. Once was all it took to confirm RED was hot and BLACK was the furance relay. EASY!