Performed furnace diagnostic on 2007 Coleman heater. Upon my diagnostic I found the customer had replaced high limit along with accidentally breaking hot surface igniter. Replace hot surface igniter and tested system, Also had to reset limit switch located in indoor blower compartment. System fired up and began to heat. upon further inspection I found that the supply vents were all covered up by furniture ultimately causing the initial failure of high limit error code. Due to the very bad air restriction occurring in the home this can cause the system to run a higher temperatures recommended that furniture is moved and filter swapped out at least 1 to 3 months. Supply temperature was coming out at 120° in system is fully operational and heating upon departure, signed customer up on maintenance plan to maintain both AC and heater once a year.