I just installed a new Circuit board in my Carrier Furnace. When I tested having only the White wire to CON and the Red wire to Y. The RED light Flashes Sold RED for 5 sec. and then flashes. The Component Test does run successfully. I'm not clear why the LED light first flashes sold for 5 sec. and then RAPID Flashing. The chart indicates a Line Voltage Polarity or twining problem. I'm not using twining so not sure how to verify Polarity if that is the issue. HELP!! Thanks.

Can you easily switch the secondary and/or primary leads of the 24 VAC transformer? Check this, if it was easy to mix the wires up during the install.

I think the transformer's secondary must be in phase with the mains.

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Originally Posted by wuswus

I just installed a new Circuit board in my Carrier Furnace. When I tested having only the White wire to CON and the Red wire to Y. The RED light Flashes Sold RED for 5 sec. and then flashes. The Component Test does run successfully. I'm not clear why the LED light first flashes sold for 5 sec. and then RAPID Flashing. The chart indicates a Line Voltage Polarity or twining problem. I'm not using twining so not sure how to verify Polarity if that is the issue. HELP!!! Thanks.

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I see from the Transformer a thin White Wire going to PR2 and thin Black Wire going to PR1. I also see from another part of the furnace a thicker White wire going to L2 and a thicker Black wire going to L1. Which wires do I switch on the circuit board?

You need to explain this first?

When I tested having only the White wire to CON and the Red wire to Y

If this is low voltage wiring the red should not be on the yellow.

Did you mark all the wires before removal from the old board?

Either switch L1 and L2 OR PR1 and PR2. Doesn't matter.

The red/white wire pair run to the Air Compressor and Red on Y and Whit on Com. When I switched the other was the 3AM fuse would blow. So, now thos wire are switched back to Red on Y and White on Com. The LED on the Circuit board is solid for about 5 seconds and then goes to flashing. The Blower does come on and Air Conditioner appears to work. The only issue now is the Furance won't come on after the Blower starts. Not sure is this is Polarity issue or some issue with the new board?

I don't want to damage the circuit board. Can switching L1 and L2 OR PR1 and PR2 cause any damage to the board?

What's the model of your furnace? I'll take a peek at the diagram online if I can find it.

What code do you think it's blinking at you?

Do you think it's possible you mixed those wires up?

The red/white wire pair run to the Air Compressor and Red on Y and Whit on Com. When I switched the other was the 3AM fuse would blow. So, now those wire are switched back to Red on Y and White on Com. The LED on the Circuit board is solid for about 5 seconds and then goes to flashing. The Blower does come on and Air Conditioner appears to work. The only issue now is the Furance won't come on after the Blower starts. Not sure is this is Polarity issue or some issue with the new board?

Since it was not explained where the wires went to I told you to move them. Sorry about that but when not enough information is available these are the kind of answers you will get.
The two wires to the outside A/C unit will connect to any of those two posts. In this case there is no polarity to worry about since it is just a simple two wire power source for the coil in the contactor/relay outside.

As mentioned before post the model number of your unit and the circuit board part number for both the new and old board.