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Hello, do you have a volt meter?
This is likely a blown fuse in the unit on the circuit board or inline from the transformer. The fuse on board would be a blade type fuse like found in a car. If inline it is a small tube fuse in the wire off transformer. Is this a YCD unit?
so C is NOT connected in the wifi stat? Or you had C connected at unit and at thermostat yet it did not power up?
thank you. And at the unit...the blue wire is actually attached to a C terminal?
And is there a rc rh in thermostat (wifi) connected with a short jumper?
is there a zone control box?
ok, we need to trace the thermostat wire from the furnace...if zoned..it goes to a zone panel first..then the the stat.
a zone panel is where we need to check for thermostat wiring...furnace wires to panel...then panel wires to thermostats
once I know what zone panel you have I can direct further
because power for thermostats comes from the panel...not the furnace...at furnace you are looking at zone panel wiring..not thermostat....the furnace wires to the panel....then all thermostats connect to the panel on similiar terminals like found in furnace...tommorrow is fine
just keep this on your end until tomorrow or it will force a response from my end. Just hold until you are ready tomorrow.
Ok we are close now...unfortunately I could not blow the pic up clearly..does it just say Ztech?
where the thermostat attaches...do you have 24v R and 24v C?
far right upper corner blue and black wire...do they go by themselves to a transformer?
And on left side do you see com?
ok, your thermostat C wires need to connect to the 24c black wire. You can install one wire and then wire nut others to it. Or if you see a 24v c or com on the board we can use that.
does the blue wire go to the furnace or to a different transformer?