Found heat not operating upon arrival. Found igniter assembly heavily charred. Replaced igniter assembly and tested operation. System was cycling on and off. Tapped on gas valve and burners turned off. Tapped on gas valve again and the burners went back on. Found gas valve intermittently failing. Replaced and tested complete operation. Let house get to set temp and ensured system turned off , then raised temp and made sure system came back on. Set propane pressure to 10.5 inh20. No further issues to report at this time.