This tells me the Therm-o-disc is shutting off too soon, and a multimeter confirms it's shutting off. I want to replace it.
I'm a little puzzled about how to select a replacement. It has L135-30 on it. I'm pretty sure the L135 means it opens it's contacts at 135 deg. F. Which seems to be pretty common from what I was looking at on the web. But what does the -30 mean? I know it turns the burner back on far above 30 deg (which would be freezing inside the house).
So, what does that -30 mean?
This sensor has the following numbers on it. 200374 T-D-D 60T11 7843 L135-30
Do any of thee other numbers mean anything, aside from factory stick numbers?
Note, the furnace is a MILLER brand, propane (mobile home) furnace from around 1979. Aside from this problem of shutting off the burner too soon, it's still in good shape for it's age. I did replace the blower motor a few years ago, and that fan-limit switch last year. Otherwise it's been no trouble.