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System turns on and off too often.

A trained HVAC tech should run these checks, and a licensed heating tech should do any burner work.

Customers put it like this

  • It keeps kicking on and off
  • It shuts off before the house warms up
  • The furnace keeps cycling
  • It runs a bit then quits
Prepare this job in ForeBotFind another guide

Stop first if

  • A rollout or manual-reset limit has trippedKeep the furnace off. Call a licensed heating tech. Find the cause before any further reset.
  • You smell gasLeave the building now. From outside, call emergency services or the gas utility.
01

Ask on the call

6

Homeowner? These are the questions a good technician will ask you. Having the answers ready makes the first visit count.

  1. How long does it run, and how long is it off?
  2. Does it happen in heating, cooling or both?
  3. Does it stop on the thermostat, or on a code?
  4. Is the thermostat near a supply vent, lamp or sunny window?
  5. Was there any insulation, window or air sealing work?
  6. When was the filter changed?
02

Bring

5
  • Watch or timer
  • Handheld thermometer
  • Digital manometer
  • Electrical meter
  • Clean filter
03

Check on site

6
  1. Log run and off times. Note what ends each cycle.
  2. Read stored codes.
  3. Check filter and registers. Work out airflow from the maker's table.
  4. Survey the thermostat location and compare it with a handheld reading.
  5. On a furnace limit trip, a tech measures temperature rise after warm-up and compares it with the plate.
  6. If controls and airflow look right, compare a current load calculation with capacity.
04

Keep on the record

5
  • Cycle log
  • Stored codes
  • Thermostat location photo
  • Temperature rise reading
  • Notes on any building envelope work

General guidance for a qualified person, not a finding about any home. The person on site decides.