My Trane XR80 furnace is only blowing cold air. The diagnostic light is bllinking 4 times.
I checked diagnostic codes and this one means (open limit device). Please clarify which part(device) needs to be replaced?

Most limit devices can be reset,, little button in the center between where the wires connect,, if it opens again,, need to figure out the cause,, maybe overheating for some reason,, they don`t go bad very often

Thanks for the quick respond. I can't find "the little button" to reset the device.
Please send me a picture or web site where to check how this looks like. Thank you.

High limit switch

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

Role out switch

http://ww2.justanswer.com/uploads/MarkHenley/2009-12-19_194201_rollout_typical.jpg


Check gas pressure and change filter if dirty.