1

My furnace is short-cycling. I've tried the following:

  • replaced the flame sensor
  • Shorted the thermostat heat demand signal
  • Checked the blower capacitor
  • Checked the air intake filter
  • Checked the exaust vent

It seems to only works after I cut the power to it for 8+ hours

When it starts working it will work for about 48 hours and then return short cycling.

It has only begun short cycling at night (maybe temperature related).

What else should I trouble shoot.

bumped to the homepage by Community 16 hours ago

This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.

  • Does it have a control circuit board? If so, couldn't it be something there? Years ago our now 27-year-old Carrier NG-fired forced-air furnace required a new board to restore function (done by our repair service). – Jim Stewart Jan 24 at 10:02
  • 1
    Hello, and welcome to Home Improvement. What do you mean by "short-cycling'; how long on, how long off? – Daniel Griscom Jan 24 at 12:12
0

I would start by trying to find a service manual for your furnace, and see if it has a troubleshooting flow chart.

I am thinking either:

  • Something is not functioning correctly, and the control board is shutting it down to prevent damage
  • A sensor is reading incorrectly
  • The control board is having issues and not applying logic correctly.

If the control board is detecting something wrong, it might throw an error code. Previous systems I've used had an LED on the board that would blink out the error code.

You might be able to check the output of the various sensors by back probing the connectors. You can do your 8 hour reset to determine the 'good' values, then test it when it is short cycling to see if these are different enough to cause the control board to think something is wrong.

Look over the control board for signs of damage - blown capacitors, burn marks.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.