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Hi I have a nordyne m1m unit and the A/C side will not work, the Heater works, but not the A/C. when I turn the A/C on the red LED goes off and the Transformer ges really Hot. any help would be appreciated

Sounds like you have a short in the low voltage wiring. The transformer should be warm but not hot. I would check the low voltage wiring for any shorts or where it has rubbed thru.

Just checked the wiring and no problem there. I am starting to suspect the motherboard

The red led light off means no power. When it does this, test across COM and 24V on board to see if you have 24-28vac.

If not, test across 24V secondary side of transformer for 24-28vac.

If you have it at the board:

Trace the two low voltage wires from the outdoor condenser contactor coil (2 small wires connected to sides of contactor).

Trace them back inside checking at all connection points for 24-28vac.


If they return back to board, see if the 24-28vac is exiting the board going to those two wires.


Because the Furnace works for Heat, the 24vac low voltage circuit is thre, but may be getting shorted somewhere along the circuit.

Find last place that it was present and the problem lies between there and next junction/connection where it is not present.



It could very well be the board.



Take care and best wishes,
Robert

Well now I am noit getting the 24VAC on the transformer, I still dont think it is the transformer. I replaced it with a new one, now is not getting Hot but is not providing poer to the unit, I have 124VAC, I belive that the circuit board is bad. This unit is nothing but Problems, and is only 4 years old

Here is the board


and the transformer

Are you saying you have 124vac on the primary side of transformer, but do not have 24vac on the secondary side (top) ?


Do the tests as detailed in previous post.



Thanks,
Robert

you mean this one?

viewtopic.php?t=408

Also the Heater is not Working now, I still do not have 24VAC on the secundary

Reread my previous posts and follow those steps. If you have 120vac at Primary side of transformer and do not have 24vac at Secondary side, the transformer is bad.


Note that another problem could have caused this and replacing the transformer only could destroy another transformer.


Take care and best wishes,
Robert

Still not working, I am ordering a new transformer, Before this all happened, the aux limit switch had gone bad, I just bypassed it, I do not belive that this caused my problem. But who knows, Robert can you be specific to what thread to look at for troubleshooting?(Link)


Thanks

Hi,

The steps I referred to are my replies in this thread.

Get a automotive type ATC 3 Amp fuse and inline fuse holder and splice it into the HOT wire coming from secondary side of transformer.


That will protect transformer should problem be a short somewhere.



Thanks,
Robert