I May Need a New Thermostat?

Old 07-30-11, 03:59 AM
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I May Need a New Thermostat?

I noticed a few days ago that the central air wouldn't always kick-in when the thermostat showed that it was above temperature and because I"ve been manually adjustring a couple of times a day, I've also noticed that it hasn't always been coming-on. Sometimes I've had to the temp back up, then back down to get it to start.

Yesterday afternoon, it wouldn't kick-off. Not only did it not stop when it was below temperature, but it also wouldn't stop when I pushed the temp up and when I turned the t-stat off. Though, once I turned it on and off a couple of times over ten minutes, it eventually stopped.

The thermostat was here when we bought the place and I'm guessing that it's 10, 15 or more years old. I could look for the receipt from when two or three owners ago bought the AC, but it also isn't brand new. The thermostat is a programmable and when I manually adjust it, I only go up or down a degree or two and I've been doing it for two years, so I know how long it takes for a manual adjustment to go through.

My thinking is that I should start by replacing the thermostat, but before I go buy one, I thought I'd ask if anyone has any other ideas of something I could check.

Old 07-30-11, 05:39 AM
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Thats a good,simple, cheap start to the diagnosis... and most likely correct since that is what controls everything and tells it when to run and when to stop. I recommend Honeywell stats...dont buy the cheap ones though. Get a good one and you wont regret it. IMO
Old 07-30-11, 07:58 AM
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It may be a battery-operated thermostat and simply need new batteries.
Old 07-31-11, 06:21 AM
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check this test out..shut OFF the disconnect out at the condenser outside,remove the stat off the subbase,furnace is still powered but pulling the stat will stop control of it and the outside condenser..now for the test have somebody out bt the condenser with the electrical panel off and the contactor viewable...take a small piece of stat wire or paper clip and touch R to Y COMPRESSOR CONTACTOR repeating it over and over have the person outside tell you if the contactor is going in and out....if it is its the stat that is tired and delaying your cooling call.then touch R to G FURNACE FAN ..supply fan should run....everytime you touch those two.if the quick cycling is good with those mini jumps the stat is semi-shot and a new digital one willl solve the problem...just for your install info the new digital stats call for a constant 24Vs at the subbase might need to catch the C side of the furnace TR for this hope you have spare wires in the stat pull i'll check back for questions about this test before noon EST

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