Hi, I have a York system about 10 years. Its control board keep giving me problem. Most last year was the connection problem of the socket where the t-stat's 4 wires go in. I finally soldered a fly-wire for the W for heating issue last winter to fix it.

Now, the summer comes and the cooling is not working. I doubled checked by shorting the R-W, the heat went on and the blower went on, everything is fine. By shorting R to G or R to Y, there was some flowing fluid noise inside the furnace, the external compressor went on and cool, but the blower will not work.

The R-G connection doesn't turn on the blower, yet it seems to turn on the compressor, or at least some fluid is running through the furnace.

How can I be certain it is the blower or the board has problem? The blower had replaced a cap last year when R-G didn't do anything including the fluid noise, yet R-W nor R-Y can make the blower run.

Thanks!

A/C blower relay on board is probably defective.

Thanks for your quick reply. If so, is changing the relay a feasible solution or the whole board?

Whole board. The relay might be impossible to find then you are still going to have to plat with a printed circuit board. Not a good thing. Get the board.