Last updated: 2026-05-01

🛠️ Can you fix this?

DIY confidence 0%

Easy — Most homeowners

🏠

Furnace Not Igniting

Thermostat calls for heat but furnace doesn't fire up

85%

85% chance this is caused by:

Dirty flame sensor or failed hot surface igniter

⏰

Fix it this weekend. Most parts ship same-day on Amazon.

A service call costs $150-300. This repair takes about 15-20 minutes and the part runs $40. Order the part tonight, fix it Saturday morning.

🔧 The Exact Part You Need

Hot Surface Igniter

$25

Buy on Amazon →

Flame Sensor

$15

Buy on Amazon →

Total parts cost: $40. Same-day shipping available on most items.

🔍

Find the Right Part for Your Furnace

Parts vary by model. Search with your model number for the best match.

Find on Amazon →

Tip: Add your model number (e.g. "GE GSS25GSH") for more precise results.

🔥 Parts for Furnaces move fast on Amazon — especially common failure parts like these.

🔨 Tools You'll Need

Multi-Bit Screwdriver

$22

Amazon →

Emery Cloth or Steel Wool

Search on Amazon

Amazon →

Easy · 15-20 minutes

Parts: $40 vs $$2,500-6,000 to replace

📋 Step-by-Step Instructions

Turn off power and gas to the furnace

Remove the front panel

Locate the flame sensor (thin metal rod near the burners)

Remove it (usually one screw)

Clean it gently with emery cloth or steel wool

Reinstall and test — if it still won't ignite, replace the igniter

Igniter is fragile — don't touch the gray element with bare hands

⚠️

Don't put this off.

A Furnace that's failing can cause water damage, electrical issues, or food spoilage — each costing 10x what the replacement part costs. The fix is straightforward. The part is cheap. The risk of waiting isn't.

Frequently Asked Questions

How much does it cost to fix a furnace that's not igniting?

The part costs about $25. If you do it yourself, that's your total cost. A professional service call would add $100-200 in labor, bringing the total to $175.

How long does this furnace repair take?

This repair is rated "easy" and typically takes 15-20 minutes. The most time-consuming part is usually accessing the component, not the actual swap.

What if this isn't the problem?

Our diagnosis is 85% likely based on the symptom you described. If replacing this part doesn't fix it, the next most common cause for "thermostat calls for heat but furnace doesn't fire up" would be related to the wiring harness or control board. In that case, consider calling a professional.

Should I just replace my furnace instead?

A new furnace costs $2,500-6,000. If yours is well under 15-20 years old, a $25 repair is far more cost-effective. If it's near end-of-life and has had multiple issues, replacement starts making more sense.

🔨 Need tools? Get parts on Amazon

Get Parts →