My furnace has both the Fan Limit switch control where I set the
pointers, and a secondary limit sensor which is the Therm-o-disc type.
I recentle replaced the fan limit control because the fan ran all the
time. The new control solved that problem. However, after the burner
begins, the Therm-o-disc shuts off the burner before the fan starts. I
had to set the Fan-on to around 90deg, which I know is too low.
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.
Do any of thee other numbers mean anything, aside from factory stick
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.