Armstrong SX 80

jchutch

Hope someone can point me in the right direction from here. I have an SX 80 with no heat. The inducer and forced air blowers run continuously. There is continuity when the pressure switch is closed, but no power. Transformer reads 120v in and 24v out to the board. No power to the thermostat (or to the block on the board that leads to the thermostat). Where else can I check before dumping $ into a new board? Thanks.

westernhvac

fuse?

hf05

Hi limit open maybe! filters clean?

DuMass

I would also start with checking the fuse on the board.
It can sometimes be difficult to see if those little 3 and 5 Amp ATO automotive type fuses are blown while they are installed. There is a little “window” on top of the fuse that normally darkens when they blow and also two tiny slots for testing with meter probes while installed, but I usually just pull them out in order to visually inspect them.
If it is the fuse, then that’s when the fun really begins, since you would want to find the reason why it blew in the first place, so it doesn’t keep happening.

If you happen to have one, you can use a mini-circuit breaker, like the “Lil’ Popper”, with the same ampere rating in place of the fuse, so you don’t end up with a pile of blown fuses from troubleshooting the problem.