The Transformer is connected to pins 4 and 3.
Pin 3 is connected to pin 2.
Pin 2 goes to the Fireman's Switch Loop and returns on pin 1.
Test for voltage from Pin 1 to Pin 4. You should get 24 VAC if the Fireman's Loop is closed.
When you get 24 VAC from Pin 1 to Pin 4, the Heater should Boot-Up.
Normal boot-up is 888, 128, and then rX, where X is the software revision number.
Test for voltage from Pin 3 to 2, Pin 3 to Pin 1 and from Pin 2 to 1.
If Pin 3 is connected to Pin 2, you should get 0 volts from Pin 3 to Pin 2.
If the Fireman's Loop is closed, you should get 0 volts from Pin 3 to Pin1 and from Pin 2 to Pin 1.
