Troubleshooting Topics:
Understanding Your Electric Furnace
Before troubleshooting, it helps to understand the key components of an electric furnace:
Heating Elements
Resistance coils that heat up when electricity passes through them (like a toaster)
Sequencer
Controls which heating elements turn on and in what order to prevent electrical overload
Blower Motor
Circulates heated air through your ductwork and into your rooms
Limit Switch
Safety device that shuts down elements if temperature gets too high
Thermostat
Sends signals to furnace when heat is needed
Control Board
The "brain" that coordinates all furnace operations
Step 1: Basic Troubleshooting Checks
Before diving into complex diagnosis, run through these basic checks. They solve about 50% of electric furnace problems:
1Check the Thermostat
- Is it set to HEAT mode? (Not COOL or OFF)
- Is the fan set to AUTO? ("ON" runs blower without heat)
- Is the temperature set higher than room temperature?
- Replace batteries if it's battery-powered
- Check for a blank display (indicates power issue)
2Check the Air Filter
- Locate filter (return air duct or furnace cabinet)
- Hold filter up to light—if you can't see through it, replace it
- A clogged filter causes overheating, triggering safety shutdowns
- This is the #1 cause of "furnace runs but no heat" problems
3Check Circuit Breakers
- Electric furnaces often have 2-3 breakers (blower + heating elements)
- Look for breakers in middle position (tripped)
- Reset by turning fully OFF, then ON
- Also check the disconnect switch near the furnace
- Warning: If breaker trips again immediately, STOP and call a pro
4Check Vents and Registers
- Make sure all supply vents are open
- Check that return air vents aren't blocked by furniture
- Closed vents restrict airflow, causing overheating
Problem: No Heat At All
Symptom: Furnace doesn't run, or runs but produces zero heat
Possible Causes & Solutions:
| Cause | DIY Fix? | Solution |
|---|---|---|
| Thermostat not calling for heat | Yes | Check settings, replace batteries |
| Tripped breaker | Yes | Reset breaker (once only) |
| Tripped limit switch | Maybe | Replace filter, wait 30 min for reset |
| All heating elements failed | No | Professional element replacement |
| Faulty sequencer | No | Professional diagnosis & replacement |
| Bad control board | No | Professional replacement (call for quote) |
For detailed diagnosis of no-heat issues, see our complete guide: Electric Furnace Not Heating: 7 Causes & Fixes
Problem: Blowing Cold Air
Symptom: Blower runs, air comes from vents, but it's cold or lukewarm
This typically means the blower motor is working but the heating elements aren't activating.
Troubleshooting Steps:
- Check thermostat fan setting – If set to "ON" instead of "AUTO," the blower runs continuously without heat. Change to "AUTO."
- Check for a clogged filter – Overheating from restricted airflow can trip the limit switch, shutting off elements while blower continues.
- Listen for a click – When the thermostat calls for heat, you should hear a click, then the elements should energize. No click = thermostat or wiring issue.
- Feel the supply plenum – After 5 minutes of running, the metal duct near the furnace should be warm. If cold, elements aren't heating.
Most likely cause: Faulty sequencer not triggering the heating elements, or one or more failed elements. Both require professional diagnosis with electrical testing equipment.
Problem: Not Enough Heat
Symptom: House warms up but doesn't reach set temperature, or some rooms are colder than others
Possible Causes:
- One or more heating elements failed – If 1 of 3 elements is dead, you get ~66% heating capacity
- Dirty air filter – Restricts airflow, reducing heat distribution
- Duct leaks – Heated air escaping before reaching rooms
- Undersized furnace – System can't keep up with heat loss in very cold weather
- Poor insulation – House loses heat faster than furnace can produce it
Diagnosis:
- Replace air filter
- Check if supply vents in different rooms feel equally warm (uneven = duct issue)
- Note if problem is worse in extreme cold (may indicate undersized system)
- Have a professional test each heating element for proper output
Problem: Short Cycling
Symptom: Furnace turns on and off repeatedly (every few minutes) instead of running through a full cycle
Common Causes:
1. Clogged Air Filter (Most Common)
Restricted airflow causes overheating. Limit switch shuts down furnace. After cooling, it tries again. Cycle repeats.
Fix: Replace filter
2. Faulty Limit Switch
A failing limit switch may trip at temperatures lower than it should, causing premature shutdowns.
Fix: Professional replacement (call for quote)
3. Thermostat Problems
Malfunctioning thermostat may send erratic signals or be in a location affected by drafts/heat sources.
Fix: Relocate, recalibrate, or replace thermostat
4. Oversized Furnace
A furnace too large for the space heats quickly, reaches target temp fast, shuts off, then restarts when temp drops.
Fix: Variable speed upgrade or system replacement
Problem: Strange Noises
| Sound | Likely Cause | Urgency |
|---|---|---|
| Humming | Normal transformer/motor sound, or blower capacitor issue | Low (usually normal) |
| Clicking | Sequencer engaging elements (normal), or relay problems | Low (usually normal) |
| Squealing | Worn blower belt or motor bearings | Medium (service soon) |
| Grinding | Failing motor bearings | High (call soon) |
| Banging/Popping | Ductwork expanding/contracting, or loose panel | Low (usually harmless) |
| Electrical buzzing | Loose electrical connections, failing component | High (call immediately) |
Problem: Burning Smell
Dusty/Musty Smell at Season Start
Normal. Dust accumulated on heating elements burns off when furnace first runs after summer. Should clear within 30-60 minutes.
Burning Smell That Persists
Check your filter. A clogged filter causes overheating, which can create a burning smell. Replace filter and monitor.
Electrical/Plastic Burning Smell
Turn off furnace immediately. This indicates overheating wiring, failing motor, or electrical component damage. Call a professional—this is a fire hazard.
Problem: Tripping Breakers
Warning: Repeated breaker trips indicate a serious electrical problem. Do not keep resetting the breaker.
Common Causes:
- Short circuit in heating element – Element has internal break causing arcing
- Ground fault – Wiring insulation damage allowing current to escape
- Failing blower motor – Motor drawing excessive current as it fails
- Overloaded circuit – Other appliances sharing the circuit (rare with furnaces)
- Wrong breaker size – Undersized breaker for the furnace (improper installation)
What to Do:
- Reset the breaker once
- If it trips again immediately, leave it off
- Call a licensed electrician or HVAC professional
- Do not use the furnace until inspected
Component Testing Guide (Professional Reference)
These tests require a multimeter and knowledge of electrical systems. They're provided for reference—hire a professional for actual testing.
Testing Heating Elements
- Power off, disconnect element leads
- Set multimeter to resistance (ohms)
- Good element: 10-30 ohms typically
- Bad element: Open circuit (infinite resistance) or very low resistance
Testing Sequencer
- Requires testing with power on (dangerous)
- Check for 24V input from thermostat
- Verify 240V output to elements in sequence
- Each stage should activate ~30 seconds apart
Testing Limit Switch
- At room temperature: should show continuity (closed)
- If open at room temp: switch has failed and needs replacement
- Some switches have a manual reset button
When to Call a Professional
Safe for DIY
- • Replacing air filter
- • Resetting breaker (once)
- • Adjusting thermostat
- • Replacing thermostat batteries
- • Opening blocked vents
- • Basic visual inspection
Call a Professional
- • Breaker trips repeatedly
- • Burning electrical smell
- • Any electrical component repair
- • Heating element testing/replacement
- • Sequencer diagnosis
- • Blower motor issues
- • Control board problems
Need Professional Electric Furnace Troubleshooting?
Our licensed technicians have the tools and expertise to quickly diagnose any electric furnace problem. We offer same-day service and 24/7 emergency repairs throughout New Jersey.
Frequently Asked Questions
How do I troubleshoot my electric furnace?
Start with the basics: 1) Check thermostat settings (HEAT mode, fan AUTO, temp above room temp), 2) Replace dirty air filter, 3) Check circuit breakers for trips, 4) Verify blower is running. If these don't solve the issue, you likely need professional diagnosis of heating elements, sequencer, or control board.
Why is my electric furnace making a humming noise but not heating?
A humming noise without heat usually indicates the blower motor or transformer is energized but the heating elements aren't activating. Common causes: faulty sequencer not triggering elements, failed heating elements, or a tripped high-limit switch. The humming you hear is likely the blower motor running normally.
How do I reset my electric furnace?
To reset an electric furnace: 1) Turn off the thermostat, 2) Turn off the furnace disconnect switch (near the unit), 3) Turn off the circuit breakers in your panel, 4) Wait 30 seconds, 5) Turn everything back on in reverse order. If the furnace still doesn't work or trips again, call a professional.
What causes an electric furnace to short cycle?
Short cycling (furnace turns on and off frequently) is usually caused by: clogged air filter restricting airflow, overheating triggering the limit switch, faulty thermostat, or oversized furnace for the space. Replace your filter first—it's the most common cause.
How do I know if my electric furnace sequencer is bad?
Signs of a bad sequencer include: no heat at all (elements not activating), only partial heat (some elements working), elements that won't turn off, or breakers tripping when furnace starts. A technician tests sequencers with a multimeter by checking voltage output at each stage.
Why does my electric furnace smell like burning?
A burning smell can indicate: dust burning off heating elements (normal at season start), overheating due to restricted airflow (check filter), failing blower motor, or electrical problems. If the smell persists after replacing the filter or smells like burning plastic/wiring, turn off the furnace and call a professional immediately.
Can I troubleshoot electric furnace heating elements myself?
Visually inspecting elements is possible (look for breaks, discoloration, or damage), but testing requires a multimeter and working with 240V electricity. Due to the danger of electrocution, element testing and replacement should be done by a licensed professional.
How long do electric furnaces last before needing replacement?
Electric furnaces typically last 20-30 years with proper maintenance—longer than gas furnaces due to fewer moving parts and no combustion. Consider replacement if repairs are frequent, multiple components are failing, electric bills have increased significantly, or the furnace is over 25 years old.