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hillm's avatar
hillm
Explorer
Sep 28, 2013

Suburban SF-25 furnace bench test

There are four wire going to the furnace.
Red is 12v+
White is grnd
Blue and blue are labeled "thermostat" in the wiring diagram

I have red and white connected to a spare 12v battery (w/inline 15amp fuse) but I don't know what to do with the two blue. Do I connect them to create a circuit? That doesn't seem right because there's 12v going to the thermostat. Any quick suggestions on how I mimic a closed thermostat on those wires?
Thanks,
Milt

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