I live in a 50's rancher. It's the typical sort of thing ie brick veneer, no insulation, aluminium windows and a hvac system from the 70's at a guess.

I know the hvac system is getting close to needing a replacement but right now it's band aids at the ready as I don't have 4k+ spare. The ac condenser has a small leak that we get by with having a company top up the freon. I know this is a bit naughty but you do what you can at the time.

Now that fall has arrived out of nowhere the ac worries are done with for the season but now I seem to have a issue with the furnace. The missus switched it one today and we got the smell of burning dust (I hope) but the blower on the furnace keeps pulsing rather than starting and running.

I changed the thermostat a month or so ago and then found out that despite wiring the thing as per the labels on the wires, it seems to be backwards. Auto = on and On = auto. I don't know if this is causing the pulsing on the furnace or not.

Anyone here with experience of furnace issues? I could certainly use some advice before having to call someone out and lose my arm and possible leg.