On 12/10/2013 2:06 PM, Danny D'Amico wrote:

Based on this discussion of colors and abbreviations, I took a closer look
and snapped this large-format picture for you to guide me:
http://farm8.staticflickr.com/7395/1...61f28c11_o.gif

As you guys noted, there seem to be 6 labelled attachment points,
with the following 4 wires connected:

R = red wire
W = white wire
G = green wire
Y = blue wire
B = nothing is attached
O = nothing is attached

Is the voltage to be expected a DC or AC voltage?
SM: Should be 24 VAC. May be as high as 28 VAC, but that's rare.

What's the range? (I'm assuming it's *not* 120VAC!)

What would you use as the ground point for the voltage test?
SM: As with our discussion of lamp timers, this thermostat appears to
only be connected to the "hot" side of the transformer. No common is
found at the stat. with a modern VOM, you can read through a load.


PS: I will jump the wires, as suggested, but first I want to see
what we have before I jump stuff.
CY: That sounds very wise. I'd read R to W, and see what kind of AC
volts you get.


PS: I don't see a fuse, but I do see a resistor.

SM: If there is a fuse, it's inside the furnace. And, yes, there is very
likely to be a fuse on the circuit board. Probably blade fuse, 3 amps.

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Christopher A. Young
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