hi i have a concord 80 plus furnace that's blowing nothing but cold air. also i noticed that the ignition coil or rod does glow and because it doesn't glow it not igniting the gas in the furnace. the green light blinks 4 times which based on the codes on the door means the limit or roll out switch is open. how can i fix this without having to call a HVAC peson. thxs

the ignitor does or does not glow? change you filter and check the high limit switch, just tap it. also there are probally 2 roll out switches follow the red wires the roleouts have red reset buttons in between the wires.

thx for the answer. where is the high limit switch and the roll out switch located?

roleouts are usually on top or on either side of the burner
http://www.mobilehomerepair.com/media/img/nordyne/626343.jpg

high imit above the burner.

http://store.hamiltonhomeproducts.com/ProductImages/limitswitches/025-29041-005.jpg

ok thx. ill check both and let you know what happens