AC themostat repair?

I have central air conditioning and being in Florida I rarely need to turn the heat on. The cooling seems to work fine. I set the thermostat to 70 and if it heats up above 70 it kicks in.
But the heater is not working fine. I set the same thermostat to 70, so the heater should kick in after it drops below 70 but it does not. I see the thermostat temperature go to 65 and it still does not kick on. If I adjust the setting to like 80, then after a few minutes it may come on, or might not. but then it will make it so hot and not turn off until it's way above 80.
Is this a problem with the AC unit or the thermostat? If it's the thermostat is this a defect that needs repair/replacement or a calibration issue? Something I can do myself or require a AC repair man?
Thanks,
MC
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What kind of thermostat? A programmable electronic or one with a bimatellic strip and mercury switch inside? Is this a heatpump system or a traditional separate heater/AC?
Ted
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miamicuse wrote:

Depending upon your "heater", it could be that you simply aren't giving it enough time to cycle on the indoor blower. The t-stat could very well be malfunctioning, but then there are several other component of the heater circuit that could cause exactly the same symptoms. Best bet is the yellow pages.
Richard Perry
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miamicuse wrote:

It would help to know what kind of thermostat you have.
I would also suggest that you not set the heat and the cool temp to the same temp. Logically you are asking it to heat and cool at 70. I would suggest at least 2 difference and 5 would be better. It will also save you some money.

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Some thermostats (actually most of the ones I've seen) have a selector for off, cool, heat, or fan only.
Have a look for a small switch wtih those options. Very few thermostats do heat and cool with the same switch setting.
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It sort of look like this one, not exactly:
http://images.amazon.com/images/P/B00069ECHM.01-AUH95GOHK7QQY._SCLZZZZZZZ_.jpg
But it is an analog thing. At the bottom is the temperature gauge with a setting for a temperature. You move it left or right to set the temperature.
On the top is the current temperature, and it is a hand showing the temperature. To the right is a analog switch to go from OFF to FAN to AUTO. And below that another switch from COOL to OFF to HEAT.
If I set the temperature dial to 70, AUTO and COOL, when the temperature rises to above 70, the fan turns on and the AC starts cooling until it dips to below 70 and stops.
If I set the temperature dial to 70, AUTO and HEAT, when the temperature dips below 70, nothing happens. If it dips to 65 nothing happens. If I adjust the gauge and reset the temperature to 80, and wait 15 minutes, it comes on, and it heats and heats and may not turn off for a long time. If while it's on, I reduce the gauge to 70, it will stop after say 5, 10 minutes.
Is it normal to take that long to start or stop the heater?
Why is the setting need to be set so high to simply kick it on?
I just need to know if this is something I can calibrate or I need a pro.
Thanks,
MC
Stormin Mormon wrote:

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The thermostat you have is an basic mechanical model and is likely old as the hills. Wouldn't you rather have a new digital one which will automatically set the temperature for various periods? That way you can have it set to automatically save energy when you are asleep or away, which will pay for itself in no time, if you use it correctly.
I'd get a new one and see if that fixes the problem. The symptoms are rather strange, but I would say it's still most likely the thermostat. And from the way it's behaving, it's not something that an adjustment will fix.
Features to look for in a new one:
how many different days you can set a schedule for. the best ones allow 4 seperate time/temp settings for each day. others only allow one setting for weekdays, another for weekends
adapative recovery - with most programmable thermostats, you set the time for the change to start to take effect. For example, if you want it to be 70 at 7AM, you have to set it to go to 70 at say 6:15 so it will have time to get there. the best ones have adaptive recovery, where you just set it for 70 at 7AM and the thermostat learns what time to start the change to get the temp there
vacation hold - all of them have a hold, which will just maintain the setting indefinitely. The best ones have the ability to specify a number of days to hold for. This allows you to set it down to say 50 while away for a week, yet have it resume before you return, so the house is at the right temp.
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MiamiCuse wrote:

You got an oldie there. Time to retire it. You can get a replacement for very little and you can replace it yourself. Ask the guy at the hardware store. Or you can pay to have someone replace it for you. I strongly suspect that the thermostat is dead and not worth trying to fix it.
Consider your options at the store. They will be able to show you what they have that will work and what each one does. Personally like the newer digital ones and I like it to adjust the temp for me day and night. In fact I don't have to tell mine if it want heat or cooling, it knows. However the basic ones also work, unlike the one you have now.
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