# Digital Thermostat Keeping Wrong Temperature

Hi - We've a digital thermostat for our geothermal unit. Yesterday, we decided to kick on central air. The thermostat says it's 28 degrees F, which is about 45 degrees off. Also this thermostat has been in the same location for 10 years. Because it says 28 degrees, the Cool setting doesn't trigger the air. The Auto setting does trigger the heat because it thinks it's only 28 degrees.
Any words of wisdom? Thanks!
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Mugg wrote:

Replace the batteries?
Replace the thermostat?
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On 5/24/2010 14:33, Mugg wrote:

Are you sure the thermostat isn't set to read Celsius? Some units allow the scale to be changed by pressing a multiple buttons simultaneously.
28 degrees C = 82 degrees F.
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My thoughts exactly
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wrote:

Yeah, but the A/C should have still kicked on regardless if in F or C. I think the T-stat might be defective because it works for heat being 28 degrees inside, but not the A/C. Digital T-stats can go bad. After 10 years it might be time for a new one.
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==========================================
You beat me to it!
Was going to post "Maybe the thing has reverted to metric". After power went off or something?
And btw although most people know this a quick (and almost accurate way) we convert from one to other is;
Celsius to Fahrenheit, double the C and add 32. e,g. (28 x 2) +32 = 56 +32 = 88
Fahrenheit to Celsius, deduct 32 and divide in half. e.g. 88 - 32 = 56, & 56/2 = 28.
Certainly close enough. Since 32 F - 0 C (Freezing) and 212 F = 100 C (Boiling water at seal level) and it avoids all this (100/180 = 0.56 units per degree rise/fall nonsense! Which just confuses everybody.
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