Vent, Valve & Volt
Vent: HVAC

What to tell the HVAC tech

A few minutes with this list before you call saves the technician time on the phone and at your house. Fill in what you can; skip what you can't see without opening a panel. If you smell gas or a CO alarm is sounding, don't fill this in: get outside and call 911.

What kind of system do you have?

Check all that apply. Many homes have a furnace and a central AC together.

What does the heat run on?

A gas pipe going into the furnace means gas or propane. A tank outside means propane or oil.

A power outage, a storm, a new filter, a new thermostat, or recent service are all worth mentioning.

Note whether the screen is on, blank, or showing a message like Cool On, Heat On or Waiting for equipment.

Trane and Carrier recommend every 1 to 3 months.

Look through the small window in the furnace door. Count the blinks and note the color and any pause. Don't remove the door to look.

What is the outdoor unit doing when the system should be running?
Ice or water anywhere?
Any smells or sounds?

A rotten-egg smell means leave the house and call 911 or your gas utility from outside.

Did a breaker trip?

Reset a tripped breaker only once.

Copy these from the data plate (the metal or foil label) on the outdoor unit and on the furnace or air handler. A photo of each label works too.

Always worth mentioning

  • Everything you already checked: thermostat settings, filter, breakers and switches. It saves the technician repeating your work.
  • Whether a breaker tripped and whether it held after one reset. HVAC.com and Lennox both treat a breaker that trips again as a job for a technician.
  • The blinking light pattern on the furnace control board, if you can see it through the door window. Carrier calls these diagnostic codes.
  • Any hissing, oily residue, or ice that came back after a thaw. These point to refrigerant, which only EPA Section 608 certified technicians can buy and handle.
  • For a furnace that turns on and off, roughly how long each run lasts. Trane gives 7 minutes as the minimum normal cycle length.
  • Whether a CO alarm has gone off, even once, or anyone has felt headachy or dizzy. Lennox lists a CO alarm among the signs of a cracked heat exchanger.
  • Whether the system is still under warranty and whether anyone has worked on it. Trane notes DIY repairs can void a warranty.
References (every fact above comes from one of these pages)
  1. HVAC.com: Furnace not igniting
  2. Lennox: Outside AC unit not turning on
  3. Carrier: Furnace blowing cold air
  4. EPA: Section 608 refrigerant sales restriction
  5. Trane: Furnace short cycling
  6. Lennox: Signs of a cracked furnace heat exchanger
  7. Trane: Gas furnace troubleshooting
  8. Trane: AC not blowing cold air
  9. American Gas Association: Using natural gas safely