Hi all, I have a Trane furnance that clicks a lot. Here is the problem. The thermometer calls for heat the inducer fan kicks on, after a while the igniter metal turn bright red, then the 4 burner fires. Moments later the main blower starts. Everything went normal as it should. The problem is after about 2 minutes it start to click randonly and coutinously for about 10 second then the 4 burner shuts off and clicking stops as well. After about 20 seconds, the igniter metal glows bright red and the 4 burner fires. And this on/off cycle continues until the set temperature has been reach. I short the limit switch and burner will continue to burn and runs without issue well over 5 minutes until I stopped it. Because its dangerous to run the system with the limit switch shorted. So my question is what cause the furance to overheat?. I put in a new limit switch, thinking its bad. But the problem continues. I take off the front cover/panel to look at the A-coil. Its clean I can shine a flashlight though it from the outside of the coil to the inside, I can even see the shadow of the fin on the palm of my hand on the inside of the coil. I turn the main blower motor and it turns freely. The air coming out of the vents are pretty strong. So what else could
cause the limit switch to kick in and what cause the clicking on the gas valve area. Any advice appreciated.