I have a wifi programmable Honeywell thermostat. Worked fine for 3 years, this morning I turned on my gas furnace for the first time this year and it would not go off, even when I set the "Heat" / "Cold" / "Off" to "Off."
Called Honeywell, and they told me to check the voltage "between the R and G wires" on the thermostat to be sure I was getting around 24 v. Not sure what they meant by testing "between the R & G wires." I've tested the R & G wires independently and they vary from 12v to 16v. I connect the COM end to a screw in the thermostat's case and the other end to the R or G wire screw. Are they suggesting that I touch the red cable to the R or G wire screw and them COM into the other wire screw?
Sorry, but I'm confused about the "between the R & G wires" comment. (Between the R & G wires is the Y wire, but I don't think that's what the tech was asking me to do. Difficult to communicate, because tech was on phone and spoke with a very strong, almost unintelligible foreign accent.
Also, why does my voltmeter sometimes read 13.0 (for instance) and at other times read -13.0? (with a minus sign in front of it).