On 10/31/2011 2:55 PM, tim birr wrote:
....

It's the round dial-type with a slider on top of the dial that you set
to desired temperature. Mercury bulb inside. It worked well until the
end of last winter, when I noticed that if I set it at 68 degrees, it
might go to 72 degrees or so until it shut down the heater.
....

Anyway, is there a way to fix this....or do I just need to buy a new
thermostat. If I buy a new one, any suggestions? I do not want one
of the programmable "bells and whistles," model.
....

You can try the cleaning mentioned, but it's not likely going to help.

If the mercury isn't nice and shiny any longer, it becomes more "sticky"
and it takes more to get it to flip, in effect increasing the
hysteresis. Happened to the old classic Honeywell here a year or so
ago; I put up with it until changed out the old system this year.

I looked some locally, the old-style are essentially a thing of the past
and while still possible, seemed that they were more expensive than the
inexpensive digitals. Contractor used a plain-vanilla White-Rodgers
(sp? "d" or no-d?) on these systems; seem fine. No idea what they are
cost-wise...

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