Saturday, September 24, 2011

From Fahrenheit to Celsius with a Sears programmable thermostat

We have an old Sears programmable thermostat, model C387-47145-1. It was installed when we bought this house and we don't have the manual for it. There is a sticker on the flip-down door to the buttons that tells you how to program the schedule and time. There's also one on the inside of the cover when you remove it. What neither of these stickers tell you how to do is change it from Fahrenheit to Celsius. Up until today, that wasn't a problem. When it showed the LOW BAT warning, I replaced the three AA batteries and it was happy.

Today I noticed that the LCD display was blank. I replaced the batteries. I don't know how long it was blank, but it was long enough to lose its schedule programming, including the Celsius setting.
I scoured the internet and found a manual for a different Sears thermostat model. It said to press and hold the two TIME buttons at the same time to switch between Fahrenheit and Celsius. Ours doesn't have those two buttons.

I found many requests from others looking for the manual for this particular model, and a few others. What I didn't find was a solution to my problem.

I walked back over to the thermostat and tried resetting it again by removing the batteries. Maybe I missed something when it first powers up. Nope.

I started pressing buttons in combination with each other. After a few minutes I saw a single number on the display instead of the usual time and temp. It said 78. I pressed buttons again, this time the single number was 26.


If you have one of these thermostats, you need to press and hold the HOLD TEMP button and then press the TIME button to toggle it between Fahrenheit and Celsius.

You're welcome. :)


  1. thanks a lot saved me a lot of time.

  2. Thanx. It also worked for me.

  3. I would like to buy you a beer! This post saved me endless amounts of time :)

  4. Thanks - had the same problem

  5. You are wonderful. You just solved my wife's mystery and rescue her from misery. Cheers!

  6. Wow, the only place on the web to find this answer. Thanks

  7. we seem to have the same model. Did this ever happen to you: No matter what we programmed it to, it defaults to 62F. We tried to press RUN, HOLD and even switched to emergency heat, nothing.... after a while still defaults to 62F.

    Thanks for answering if you know what to do!

    1. Hi there... I've never seen that happen. I'm not sure what to suggest, except that perhaps the thermostat is defective and needs replaced.

  8. Thank you! Finding your solution was an early Christmas Gift.

  9. Thank you Scott! Your solution did the trick!

  10. Thank you Scott! I appreciate you posting this solution.

  11. Great help! I had accidentally pressed these buttons when I removed the face plate.