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12 volts at primary limit switch, 24 volts out at transformer 24 volts at c & w terminals when stat calling for heat. furnace will not light, trouble codes call for bad primary/secondary limit switch

  • What make and model is the furnace? – ThreePhaseEel Apr 21 at 2:53
  • lennox merit series model g40uh-36b-090-07 – sparks50 Apr 21 at 4:51
  • Is that 12V from a limit switch terminal to ground, or 12V across the limit switch? – ThreePhaseEel Apr 21 at 4:52
  • 12V from limit switch to ground, on each side of limit switch, 0V across limit switch. – sparks50 Apr 21 at 16:22
  • also when disconnected limit switch has continuity, (not open) – sparks50 Apr 21 at 16:24

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