We have a ~9 yr old Kenmore gas oven/range (runs on propane actually),
and the oven temperature sensor appears to be flakey (the actual
temperature in the oven is definitely flakey). The oven has a knob to
set the oven temperature, and a digital display that shows the
temperature you set, but it does not display the measured oven
temperature - it only has a light that indicates if the oven is
"preheated" (at the set temperature).

The oven heats up to the desired temperature just fine (as measured by
an oven thermometer) and the "preheated" light comes on, but at some
point, the temp inside the oven will drastically decrease, with no
external signs of trouble. The "preheated" light remains on and no
error code is displayed. With an oven thermometer in the oven I can
confirm that the oven does get up to the set temperature as expected,
but if left on for a while, it will at some point cool down way below
the set temperature. For example, I set it to 375. It warms up just
fine. I start baking something. I check on it 1/2 hr. later and the
temp is down at 250! The oven seems to think everything is OK
though; the "preheated" light is still on and there is no error code
displayed - I'm not even sure if this model has error codes to
display. At this point, if I turn the oven temp knob to off and then
back to my desired temperature, it will then notice that the oven is
too cool and warm it up again.

I can order a replacement temperature sensor and install it, but
before I shell out the $75 + S&H (which seems like a lot), I'd like to
know that the problem is most likely the sensor and not some obvious
other problem.

So, does this behavior sound like a faulty temperature sensor?

Thanks.

-Jonathan