My furnace is tripping the high limit. It is a Downflow Payne 90+ have replaced the limit switch. I pulled the blower door off and checked all vents to ensure they are open and it still short cycles. I also changed the speed on the blower and checked gas pressure. I'm stumped! Does anyone have any ideas as to what's going on?
The only way the plenum can get hot enough to hit the high limit is lack of air flow. Open all registers and dampers and take the filter out. If it still gets too hot your central air "A" coil may be plugged with dirt.