I have what looks like an ancient Honeywell Chronotherm III running my heat/ac system here at home. For the last 2 years it has operated without problems, however over the last couple of days it has started to act up.
It seems that it will no longer hold the temperature when the system is on the A/C. I set the slider to "Cool" which engages the A/C, then press hold and select the desired temperature. Usually this would turn the A/C on and off automatically to maintain the temperature I had entered. Not any more...
What happens now is that the screen displays:
(replace 1:18pm with whatever the current time is)
The A/C is running, but will continue to run until I go down to the basement and shut it off at the shut-off, (regardless of the temperature setting on the thermostat) otherwise we'd be living in an icebox by now.
I've tried changing the batteries in the thermostat but to no avail...does anyone have any ideas as to what I can try next, any help would be very gratefully recieved!
Thanks in advance!