I'm working on a a/c and heat unit that sit's on top of the roof. Before I replaced the old mercury t-stat the a/c functioned properly but the heater did'nt. I replaced the t-stat with a LUX 400 series low voltage t-stat, I have replaced the contacter in the unit along with the step down transformer and also replaced the ignition module and gas valve with a pilot ignition system (712 series flame rectification). Now nothing works the fan,heat,and a/c, I have 120v at the contacter the 24vac coil has the 24v, the transformer has 120v going in and 24v coming out whitch feed the pilot ignition system and t-stat, they also have 24v I also double checked my wiring and it's all correct. Am I missing something or doing something wrong.

Does it have a circuit board in it? If so check for a automotive type fuse, is it there and OK?is it coding (blinking light), the model number would help if you can find