Furnace Won't Turn On? Check These Things First

NO HEAT • FURNACE TROUBLESHOOTING • HOMEOWNER CHECKS

The house gets cold.

INDOOR TEMPERATURE 65°

→

THERMOSTAT SET TO 70°

→

FURNACE RESPONSE Nothing.

BEFORE ASSUMING THE ENTIRE FURNACE HAS DIED There are a few reasonable homeowner checks that may help explain what is happening—or give your technician a much better starting point.

01

Check the Thermostat

Start embarrassingly simple.

FIRST QUESTION Is it set to HEAT?

MODE Thermostat is set to heat

TEMPERATURE Requested temperature is above room temperature

POWER Thermostat display is functioning

BATTERIES Replaceable batteries are working

Simple thermostat issues account for more confusion than homeowners like admitting.

02

Check the Furnace Switch

Many furnaces have a service switch that looks surprisingly similar to an ordinary light switch.

LOOKS LIKE A normal wall switch

≠

ACTUALLY CONTROLS Power to the furnace

Someone storing boxes, cleaning or working in the mechanical room may accidentally turn it off.

SIMPLE CHECK Make sure the furnace has power before assuming the equipment itself has failed.

03

Check the Breaker

Look at the electrical panel for a tripped furnace breaker.

BREAKER TRIPPED Reset once

→

STAYS ON? Observe furnace operation

→

TRIPS AGAIN? Stop

DO NOT KEEP RESETTING IT Repeatedly resetting an electrical protection device is not troubleshooting. If it trips again, have the problem evaluated.

04

Check the Filter

A severely restricted filter can contribute to furnace operating problems.

DIRTY FILTER Airflow becomes restricted

→

FURNACE Operating conditions can be affected

If the filter is obviously overdue, replace it with an appropriate filter for the system.

But do not assume every no-heat call is caused by the filter.

05

Check the Exterior Furnace Vents

Some high-efficiency furnaces use exterior intake and exhaust piping.

Snow, leaves or other debris can create problems if those openings become obstructed.

VISUAL CHECK Snow accumulation

VISUAL CHECK Leaves or debris

VISUAL CHECK Obvious exterior obstruction

KEEP THIS A VISUAL HOMEOWNER CHECK Do not modify venting, alter piping or dismantle furnace components.

06

What Is the Furnace Doing?

Listen.

The difference between “nothing happens” and “it keeps trying to start” can be useful diagnostic information.

CLICKING Repeated attempts?

CYCLING Starts and stops?

BLOWER Fan runs but no heat?

SILENCE Absolutely nothing?

IGNITION Attempts to light?

YOU DON'T NEED TO DIAGNOSE IT Just noticing what the furnace does after a call for heat can help the technician understand where to begin.

07

Error Codes Can Help

Some furnaces display diagnostic lights or codes.

SEE A CODE? Take a photo.

If it can be viewed safely without opening restricted equipment compartments, that information may be useful to the technician.

FURNACE FAILS Diagnostic code appears

→

TAKE PHOTO Preserve the information

→

TECHNICIAN Has another diagnostic clue

Avoid repeatedly cycling furnace power just to clear the code. That information may help explain why the system stopped.

08

Don't Keep Resetting the Furnace

Resetting something once may restore operation.

Resetting it ten times is different.

ONE RESET May restore operation

VS.

REPEATED RESETS May erase clues without fixing the failure

If the furnace keeps failing, something is wrong.

What About the Gas Supply?

If you suspect a natural-gas problem or smell the distinctive sulfur or rotten-egg odor associated with natural-gas odorant, stop DIY furnace troubleshooting.

POSSIBLE NATURAL GAS LEAK

Leave immediately.

01

Leave the building immediately on foot and tell others to leave.

02

Do not use electrical switches, appliances, phones or anything inside that could create a spark.

03

Once safely away, call 911 and your natural-gas utility.

CENTERPOINT ENERGY — MINNESOTA GAS EMERGENCY 800-296-9815

Natural-gas safety guidance: CenterPoint Energy — Smell Gas? Leave Fast

When to Call

Call Air Comfort when:

NO START Furnace will not start

SHUTDOWN Furnace repeatedly stops

ELECTRICAL Breaker repeatedly trips

ODOR System produces an abnormal smell

NOISE Severe mechanical or electrical sounds

TEMPERATURE House keeps getting colder

BASIC CHECKS DIDN'T RESTORE HEAT? That is the point where troubleshooting becomes a diagnostic service call.

Tell Us What You Already Found

When you call, tell us:

01 Indoor temperature

02 Thermostat setting

03 Whether the thermostat has power

04 What the furnace does when heat is requested

05 Any error code

06 Unusual noise or smell

07 Whether the breaker is tripped

GOOD INFORMATION = BETTER STARTING POINT You do not need to diagnose the furnace before calling. A few observations can simply help us understand what happened.

BASIC CHECKS DONE AND STILL NO HEAT?

Now Let's Find Out Why the Furnace Isn't Starting

Air Comfort Heating & Air Conditioning helps homeowners throughout Anoka County, the North Metro and surrounding Minnesota communities diagnose furnace startup failures, repeated shutdowns, airflow problems, electrical issues and other no-heat conditions.

You do not need to take the furnace apart before calling. Check the safe basics, tell us what you observed, and let the diagnostic work start from there.

CALL 763-753-6623 REQUEST FURNACE SERVICE

FREQUENTLY ASKED QUESTIONS

Furnace No-Heat Questions

Why is my thermostat calling for heat but the furnace isn't running?

Thermostat, electrical, ignition, control, airflow and equipment problems are all possibilities. Basic homeowner checks can rule out a few simple causes, but a furnace that still will not operate needs diagnosis.

Should I reset the furnace repeatedly?

No. If the furnace repeatedly fails after being reset, an underlying problem should be diagnosed instead of repeatedly cycling power.

Can I photograph my furnace error code?

Yes. If the diagnostic light or code can be viewed safely without opening restricted equipment compartments, a photo may provide useful information to the technician.

Natural Gas Safety Reference

If you smell natural gas, follow your utility's emergency instructions rather than continuing furnace troubleshooting.

CenterPoint Energy — Natural Gas Safety