We've noticed that the blower in our house HVAC system has been
running nonstop for a day or so. The thermostat was set to HEAT, fan
set to AUTO, and the ambient room temp was comfortable and well above
the thermostat setting. Logic told me the blower fan should not have
I pulled the cover off the thermostat, and it has what appears to be a
bi-metal spring coil with two mercury switches. Moving the mechanical
thermostat lever up and down didn't seem to be doing much at all. I
moved the lever way down to its bottom limit, around 50 degrees or so,
and the blower just kept running for at least an hour until I
intervened again. Then after some trial and error I discovered that
if I pulled slightly outwards on the lever as I move it, then the
coil/mercury switch assembly rotates with it.
After thinking about it for a minute, I realized that maybe that
assembly is supposed to always rotate with the lever in order to
adjust the desired temperature setting? After more trial and error, I
think I've matched the temperature indicated by the lever location to
the actual room temp (ie, when the ambient room temp drops below the
indicated thermostat setting, the blower and heat pump turn on) by
moving the lever with and then without turning the mercury assembly.
So now I think everything's working OK, except that I can't adjust the
thermostat setting without removing the cover and pulling the lever
outwards slightly to get it to "grab" the switches so they rotate with
it. The heat pump comes on now when the temp drops below the
thermostat setting, and it seems to maintain that temperature properly
and shuts off when the ambient temp is reasonable. So it seems to be
working except for not being able to adjust the temperature setting.
Does this all make sense and sound correct? Or am I out in left
field? Any (helpful) suggestions are appreciated as to what my
next step should be...
(btw, house is 14 years old, HVAC system is the original Rheem forced
air heat pump, works like a champ knock on wood except for the