Thanks, I'll definitely check that. The wires were installed on the new board the same way they were on the old one. I did some investigation online after posting earlier. Twinning seems to be hooking 2 furnaces up to basically act as one furnace sharing all the same ductwork and thermostat. I definitely don't have anything like that. I suspect the error the led is flashing is somewhat misleading. Guess I just have to keep looking for something else wrong.

I am sure I checked all the limit switches. Since the switches are hooked up in series I checked at each end of the circuit that goes through all the switches also and it is not open.

I know what twinning is. Did it back in the 70's with Bryant furnaces.

Electronics are very sensitive to in simple terms positive and negative reversal. That is why I mentioned that the transformer wires might have been switched OR that could also be why the new board is doing the same as the old. Just a thought.

I appreciate the help and I will definitely be checking to make sure the wires are connected correctly.

Maybe a call to York or whomever makes the board would help explain what will set off that code. I have had good luck with York's support.

Hvac100 appears to have come up with the fix on the new circuit board. I reversed the secondary wires from the transformer and the furnace is working. Thanks for the help.

Glad you got it going

Reversed polarity can be a pain. Just glad hvac was here to help you out. Great job hvac.

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Originally Posted by mygirlsdad77

reversed polarity can be a pain. Just glad hvac was here to help you out. Great job hvac.

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Being in this industry to long can have its advantages and disadvantages. LOL

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Originally Posted by hvac1000

Being in this industry to long can have its advantages and disadvantages. LOL

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You really should get some formal dinner plates. They are much easier to eat from and wash. :D

Nice call on the reverse polarity.

Thank you

Hvac, I don't laugh or even smile much. But that pic just made my day. The sad part is, someone has probably actually done this.

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Originally Posted by mygirlsdad77

hvac, i dont laugh or even smile much. But that pic just made my day. The sad part is, someone has probably actually done this.

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I use some of those type things in class. They always get a chuckle.

New style heat and smoke detector combo unit.