I posted a question about my AC thermostat a week ago, the cooling was
working fine but heating was not. The heater will not turn on even when I
set it all the way to a low temperature (current temperature is say 70, I
set it to 60, it will not turn on, but it may two hours later...) I called
the AC company who installed it and they came out for a service fee of $100.
By the way this is the thermostat I am talking about, a real old one. It is
a White-Rodger mercury switch.
Inside view after cover is removed:
Back of front cover:
Close up view of a sticker which should have the detail product information:
Close up view of the mercury bulb:
I am not sure exactly how things work. The technician told me that my AC
unit itself is working perfectly (LENNOX CB301-46-1P). However the
calibration is off. He says my problem is the dial probably adjusted too
far off. He showed me how to adjust the back cover dial to the current
temperature (he says it feels like 72 so he sets it to 72). After the
adjustment he left the cover off and showed me that if I push the bottom
dial to the left, the mercury bulb will tilt to the right and after 1 minute
the AC turns on. So the AC is working properly and the mercury is working
fine. He did tell me he can install a new digital thermostat for me the
unit itself will be $150 and installation $100, he did say the same unit
would be like $20 at HD and it can be easily done by myself.
So now, when I remove the cover and push the dial all the way to the left
and the mercury bulb tilted all the way to the right, the heat did not turn
on with settings set to AUTO and HEAT. After waiting like over an hour, it
finally turned itself on (for what reason I have no idea). The cooling side
worked fine, as soon as the bulb tilts right, there is a tiny spark and it
kicks on. The heater side did not. I have no clue why it worked perfectly
while he was here.
So now my option is to call him back (which means losing a whole day of
work - appointments are like 10AM - 3PM anytime in between...and pay $75),
buy a new thermostat myself and see, or play with the calibration a bit more
myself. But I don't think it's just calibration if I tilt the mercury bulb
all the way to the right and the heater does not turn on.
The only problem is with buying a new thermostat is to figure out which one
to buy. I browsed HD's catalog and they carried LUX and Honeywell? Any
specific models recommended? What should I watch out for when wiring them
besides turning off power? Is it a simple color coded 1 to 1 wiring or a
different model may require something different?