Goodman rooftop unit blowing transformers

[DbincAlan]

Hey everyone first time posting on here booing for some help or insight. I have rooftop unit manufactured by Goodman that has been blowing transformers. This job was thrown on my lap and I have quite a bit of experience with residential heating equipment but limited experience with rooftop units.

Tech support is at a loss as we have tried and replaced everything they thought it could be. I have spoken to their electronic engineer, my former supervisor with 24 years experience and my boss with 46 years are all at a loss.

It does not blow the fuse on the board and we have put a fuse inline and it did not blow either. The unit will fire up and run until the fan should kick in but the transformer blows. If you push in the contactor the fan fires up beautifully but won't turn on through the board.

Have replaced: electronic board, contactor and transformers( 3 to date)
Have eliminated the thermostat wire and hooked one up on the roof
Voltages have been gone through with tech support numerous times

Please help

[Admin]

Which side of the transformer is blowing, the primary or secondary?

[Porcupinepuffer]

And since we're talking about a rooftop, have we confirmed we have the correct single phase or 3 phase wiring and correct voltage? We've had incorrectly sent rooftops of the wrong voltage. I know you mentioned going over it with tech support, but throw the numbers at us. Once you've installed a new transformer, have you checked its low voltage before turning anything on to confirm it's in the right area?