Hello.

Recently, the fan on my AC unit stopped working. I do not have a heat pump. I have a gas heater / air exchanger combo unit in the attic, compressor outside of garage. I called an AC guy out to take a look. He told me my control board fried and I needed a new one, but he would have to order it. As I was leaving town, and didn't know when I'd be back, I decided to order it and replace it myself. The new board looks very similar to the older one, except that it is encased in plastic, which mounts to the sheet metal. Whereas before, the old board mounted directly to the sheet metal via plastic push on connectors.

Anyway, I installed the board and moved the wires and connectors over to the new board, mounted it and switched the AC fuse power back on. But nothing. I notice, however, that when I depress the cover safety switch (so that the unit thinks it's all closed back up) the board has a diagnostic LED blinking. The light blinks at a rate of about 1hz, and the board states that this equates to:

normal no call for heat

I do hear the liquid surging through the coolant line, as the outside compressor is still doing it's job, but the new board is not turning on the fan.

I have noticed a similar post on this site about switching out cnt2798 with cnt03797. Unlike that guys AC worker, my AC guy did not "hotwire" the fan to allow me to at least have air flowing until the board could be replaced. The person in the other post seemed to make that particular board work, so I have to assume the new board is a suitable replacement for the 2798. The old board was definitely bad. It had a sizeable scorch mark on the back side when I removed it.

I noticed an unplugged white wire hanging out of the way when I pulled the old board. It was a thicker wire (about the thickness of the wires that attach at the left side of the board via push on connectors. The new board has two connectors on that side that the old board did not have. I cannot tell what they are right now, as I am out of town again and hoping to get this working upon my return.

I know it was a bad idea, but I reasoned that the thickness of the white wire indicated there was a significant possibility that it connected in the area of the others (left side). So I tried both of two available spots. One location caused a small motor (maybe with a fan?) located on the heater side of the unit to turn on. The other location did nothing. I decided to look for help before playing with it any more.

One thing I need to doublecheck is the wire crossover. The multiwire connectors were a no-brainer, but I did a 1-1 "location to location" crossover of the wires, instead of "label to label" crossover. I'll doublecheck to make sure I did an A-to-A switch upon my return.

Is there any other advice you can give that could help me determine why I still have no power to the fan? Does the "normal no call for heat" LED indication tell me it's wired incorrectly?

Thanks in advance for any attention to this matter.