[Paul11]

I can start the outside ac unit by pressing the button on the contactor manually, so I have power to the unit, but it will not turn on via the thermostat switch. Also, I can't get the fan to turn on at all. I have tried bypassing the thermostat by connecting the wires and can't get the ac or the fan to turn on. Any help would be appreciated.

[mygirlsdad77]

Did you bypass the stat at the stat, or at the furnace control board? Sounds like you may have a power issue at the furnace. Check furnace breaker, ssu fuse, and 24v fuse at furnace.

[Paul11]

did you bypass the stat at the stat, or at the furnace control board? sounds like you may have a power issue at the furnace. check furnace breaker, ssu fuse, and 24v fuse at furnace.

I bypassed at the stat. I have power at the outlet where the furnace is plugged in. Where do I find the ssu fuse(what is that?) and the 24v fuse?

[mygirlsdad77]

If your funace pluggs into an outlet, you most likely don't have an ssu/fuse (ssu is just a disconnect that looks like a light switch and holds a round screw in fuse, see pic below). The 24v fuse would be either on the control board, or on secondary side of the transformer. Some older furnaces don't even have a low voltage fuse. If this is the case with yours, you will want to check for power into and out of the transformer. Should be 120v in, and 24v out. Good place to start. You can also check for 24v between r and c on the control baord, or area where stat wires hook.