I replaced the thermistor, then the gas ignitor which were easy to get to once the drum was out. The gas is still not igniting so not sure where to go from here. Putting the drum belt back on took some muscle. But then I'm 71.
Called LG on the phone and they gave the button presses for diagnostics, which then gave the HST code, saying the Humidity sensor was bad. The part was described as the Humidity sensor module. Actually it's just the wire leads for the sensor which must be electronic and only accessible by disassembling the dryer. There were descriptions about cleaning the wires, perhaps because some people use dryer sheets which cause a buildup on the wires and prevent them from doing their job. I use wool balls and have no buildup on my wires and replacing them did not fix the sensor, because the module accessible inside the dryer is not the moisture sensor, but only the wire leads.
Repair was easy, but the part does not come with directions. It is pretty self explanatory if you are used to taking things apart and fixing them. Otherwise there are YouTube videos you can pull up. Dryer runs like it is new again though and it was way cheaper than buying a new dryer.
FIRST REMOVED THE LID ON TOP OF DRYER.THEN THE CONTROL PANEL AND THE STEAM TRAY. HAVE TO UNCLIP TWO HARNEST CONNECTORS. REMOVED THE FACE PLATE THAT HOLDS THE DRYER WALLS TOGETHER ALSO REMOVE TO SENSOR HARNESS CLIPS. .REMOVED THE BELT FROM MOTOR. TOOK DRUM OUT . UNCLIPPED MOTOR COLLAR SNAP CLIPS DISCONNECT THE MOTOR HARNESS. INSTALL NE MOTOR AND CONNECT HARNESS INSTALL CLIP . REINSTALL DRUM AND PUT BELT ON. CONNECT HANESSES AND INSTALL FACE PLATE. INSTALL CONTROL PANEL AND THE TOP LID.
The installation of the gas orifice was actually simple. Unscrew the old orifice and screw in the correct orifice. Tricky part of the process was accessing the area of the gas valve.
Followed YouTube video repair process. The only problem is that the door hinge has plastic bushings attached. A couple broke and the parts listing does not show the bushings, nor does the hinge come with them. The door is a bit loose without them. Nonetheless, the repair did the job for now.
Persistent smell of propane despite multiple duct cleanings.
Despite the young age of this dryer, and failure of all the other trials to fix the problem, I figured maybe the igniter is the problem. Ordered one. Followed a U tube video to take the unit apart. Noticed immediately that there was lots of lint pretty much everywhere inside the cabinet. Come to find that the blower and the vent had never been connected, with about two inches gap. So, some of the exhaust was going out the vent hose, but lots was not. In fact, lint had coated the propane jet and the air mixer assembly. Replacing the igniter was not particularly difficult, once the dryer was in lots of pieces. I did not test the igniter before replacing it. I did connect the vent outlet to the blower and secured it. End result was a perfectly functioning unit and a happy wife. I don't recall reading about this as a possible cause of propane odor and failure of the unit to heat up.