I've quickly blown two 110 to 24v 40va transformers. This transformer powers the electronic dampers from my furnace. I have 2 zones, 2 thermostats. I've also had problems blowing the 3amp fuse in my furnace itself when activating my zone 2 thermostat. All three of my damper motors test out OK, as well as the main board for the damper controls. Could a wire from my zone 2 thermostat cause both these problems even if they test positive for continuity? Also, since my 40 va transformer is rated to 1.67 amps, should I use a 1.5 or 2v inline fuse? Thanks thanks thanks! Ethan

The wires could have OK conductivity. What you need to do is make sure the resistance between them equals the resistance of the motor or whatever they feed. I lost a couple of transformers after chipmunks chewed the insulation off my thermostat wires. Try to inspect the wires their intire length. Use the 2 amp fuse. It should still blow before the transformer burns out. Might add up the loads and make sure the transformer has a little margin over the total at any one time.