I have a goodman furnace and just the other night I noticed the house wasn't heating, I checked the furnace and the indicator light suggested vent blockage checked the vent stack that leads to chimney and found 2 dead birds in stack removed them and started furnace, thought I had it fixed. All worked fine for about 5-8 minutes. Then kept cutting itself on and off again every 5 min. indicator light now says open limit switch/check limit switch.
Don't have manual. What am I looking for? Where would it be? If I find it, what do I do? Appreciate any advice I can get! Thanks

Check filters and blower, plugged evaporator coil or secondary heat exchanger. Furnace is overheating because not enough air is going through it to keep it cool.