We had an appliance tech from the company we purchase our propane from come out an take a look at the machine. He basically said, "I have no idea - either spend $500+ with me replace a lot of parts or go buy a new machine." I paid him $75 for his advice and may buy a new machine, but I'd sure like an answer first.
For new readers - I have a gas dryer that failed to turn off the gas flame with the door open, the switch on off and the machine unplugged. The gas was not cycling, as it should, which did create overly hot laundry. Then my wife discovered that the flame was still on even with the machine shut off. She unplugged it, and when that did not turn the flame off, she shut off the gas valve.
Since this happened we have run the machine cautiously and it has worked perfectly every time.
Tonight I pulled the thing apart and had a good look inside. There was nothing unusual; no burnt wires, lose connections. not even excessive lint build up. (I had cleaned the insides three years ago when I installed a new drive belt.) I was suspicious of the valve relays and I found a good video that showed, not only how to replace them, but how to test them with an ohm meter. I did this with the following results:
Contact Spec Read
L-C 1.400 1.027
C-R 1.900 1.281
L-R .550 .521
L-R 1.200 0.943
So none of these look too good, but the normal failure mode for these is that the unit will not turn on, not fail to turn off. So far I've not found any posts related to a dryer failing to turn off. One would suppose with all the safety switches on the thing, staying on would never happen. I guess it rarely does.
I'm thinking this has to be a valve or valve-related issues. Would replacing the relays help? Replacing the valve body itself is expensive and only recommended for a gas technician. If the valve body can be determined to really be the problem, a new dryer is certainly in order. I can't see how any of the electrical switches would cause the flame to stay on, but I can see how, if the gas valve was stuck in the open position, the flame would stay on - even with power totally cut off.
And this raises the question: Could the gas be left on with the flame off? That would be a serious explosion risk!
Any input on this would be greatly appreciated.