How do you get the furnace to turn on if it’s 93F in the house, and the thermostat only goes up to 89F? Quite the conundrum.
run the ac first…
In the summer I always run the AC first.
Bring the interior temp down and then check the furnace.
The thermostat reads 72F…just turn it up.
Turning it to the on position will be a good start.
Put a cool towel over it; Pull the cover and prop the mercury bulb; Pull the cover, loosen the base screw and rotate the base (don’t forget to put it back to level).
To time consuming just jumper the white wire to the red;-);-);-);-)
I used to carry a jumper wire but was always nervous that I’d mix my colors, since it’s so rare a situation.
There is only one wire to the thermostat that is a common neutral (that would be on thermostats with lights or digital displays).
There’s always a possibility that some idiot wired up thermostat, but regardless of the color of wire the terminal that the wire connects to would indicate the common.
If you flick the jumper and it sparks a large spark you hit the common neutral. All other wires are parallel circuits and will not be affected by the jumper.
Normally the red wire is hot, but if you are jumping across the thermostat terminals without disconnecting them (at the thermostat or the equipment) the equipment may turn on by jumping other wires which have acted circuits due to the thermostat settings (i.e. the reversing valve’s sometimes remain energized and jumping the fan and compressor contactor terminals may energize the contactor).
There is a chance to take out the primaries in the transformer if you get it wrong, but with the energy so many people utilize to try to figure out temperature differential testing (which is much harder than jumping thermostat control wires) inspectors chances of getting it wrong is insignificant compared to trying to diagnose performance with an infrared thermometer.
If one were really a scaredy-cat about breaking something, installing an in-line fuse in your jumper cable will alleviate that potential threat.
Ice cube or can of circuit cooler if you don’t want to jumper.