Speaking Of My Sick Furnace

Maybe some of my smart readership can help.

It quit working the other day. I went in and looked at it, and the wiring from the thermostat had lost all its insulation and was extremely oxidized–it looked like a long, anorexic green worm. I figured the problem was that it had quit conducting, and replaced the bad sections with new wiring.

No joy.

I’ve an electronic thermostat (about ten years old or so), and it indicates that it’s working (the temperature LCD flashes when it’s supposedly telling the furnace to burn). I’ve always thought that the voltage on these things is supposed to be 24VAC, but when I disconnected the wiring and measured it, it was only fourteen. Is this indicative of a problem? Is it possible that the wiring was OK, and that I have a different problem? Like a bad thermocouple?

Does anyone have any theories, and experiments I could run?