My experience is with the Dometic fridge, but occasional a bumpy ride would dislodge the plug that goes into the back of the piezo igniter button. Mine was accessible via the radio port and would be just resting on top of the insulation. The simple fix was to bend the small finlike catches to provide more friction to the plug which resembles a narrow RCA type.
I believe the Norcold is a 300 series and the manual is found here:
http://www.thetford.com/LinkClick.as...id=290&mid=867
Maintenance checklist including thermocouple positioning is on page 8 and interesting enough, Norcold recommends AC operation above 5500 feet because of "reduced cooling performance" and "burner outages".