[BethAnn]

Carrier furnace Model #58MCA100-16 was off (new house for me). In starting it up for the first time, I turned on theexternal gas valve but failed to turn on the internal gas valve. The furnacestarted up right away but after a few minutes it stopped running. LED code33 appeared (Limit or Flame Roll-Out Switch is Open). This has since changed to Code 13 (Limit or Flame Roll-Out Switch Lockout). I have been unable to clear this lockout.

Wondering if is the flame roll-out? the Limit switch? I can't seem to find the limit switch.

 

[how]

Turning on your furnace without turning on the gas valve would usually result in a code for flame sensor/ignition fault and the furnace would lock out. Your codes indicate that there was a probable fault before the gas was turned off.
Roll out switches activate if the combution flames are not properly contained within the combustion chamber and the limit trips if it was overheating.
This sounds like a good furnace to have serviced.