Ignition Systems 101 for Homeowners: HSI vs. Spark & the Most Common Failures

Eco Heating & Cooling – Serving Dothan & the Wiregrass Area

When the temperatures drop in Dothan, Headland, Ozark, Enterprise, and the rest of the Wiregrass, homeowners rely on their heating system to fire up quickly and keep their home warm. But what happens when your heater clicks, tries to start, and then… nothing?

One of the most common reasons a furnace or heat pump with auxiliary heat won’t start is an ignition system failure.

Ignition systems are what “light the fire” inside gas furnaces. Whether your unit uses a Hot Surface Igniter (HSI) or a Spark Ignition System, problems in this part of the furnace can shut down your entire heating system. Understanding how these systems work—and the most common issues—helps homeowners know when it’s time to call a trusted HVAC professional like Eco Heating & Cooling.

What Is an Ignition System?

Your furnace can’t heat without a flame. The ignition system is responsible for creating that flame safely and reliably. Modern furnaces use one of two ignition types:

1. Hot Surface Igniter (HSI)

2. Spark Ignition System

Both achieve the same goal: lighting the gas burners. But they do it very differently, and each type has its own common failures.

Hot Surface Igniters (HSI): How They Work

An HSI ignition system is the most common type used in today’s mid- and high-efficiency furnaces. If your home in Dothan or the Wiregrass was built after the early 2000s, there’s a good chance you have one.

How HSI Ignition Works

An HSI is a small, ceramic igniter that glows bright orange when energized.

Think of it like a super-powered lightbulb filament.

When it gets hot enough (about 2,500°F), it lights the gas as it enters the burners.

Advantages of HSI

• Very reliable

• Quiet operation

• Efficient

• No pilot light to relight

But HSIs Do Have Common Failures

Because the igniter gets extremely hot every time your furnace cycles, it can wear out over time. The number-one reason for heating service calls in the Wiregrass area during winter is a failed hot surface igniter.

Most Common HSI Failures

1. Normal Wear and Burnout

HSIs are considered a “consumable part.”

Like a lightbulb, they eventually fail.

When the igniter cracks or burns out, your furnace will try to start but won’t ignite the gas.

Signs:

• Furnace tries to start but shuts off

• You hear the furnace click, but no heat comes out

• A flashing light code on the control board

2. Improper Handling During Previous Repairs

HSIs are extremely fragile—oil from human hands can damage them.

If a past technician touched the igniter with bare fingers, its lifespan may have been shortened. Eco Heating & Cooling always installs igniters correctly and safely to avoid premature failure.

3. Voltage Issues

If the furnace isn’t receiving proper voltage, the igniter may never heat fully.

This can be caused by:

• Loose wiring

• Weak transformer

• Control board issues

4. Incorrect Igniter Type Installed

Not all HSIs are the same. Some require lower voltage, some higher. Using the wrong igniter is a common cause of repeated failures—especially in older units found in Dothan, Slocomb, Ashford, and other Wiregrass homes.

Spark Ignition Systems: How They Work

Some gas furnaces (especially older models or certain manufactured-home systems) use spark ignition.

It works much like a gas grill: a spark lights the gas to ignite the burners.

How Spark Ignition Works

• The furnace calls for heat.

• A spark igniter clicks repeatedly.

• The gas valve opens.

• The spark ignites the flame.

Advantages of Spark Ignition

• Works well in older furnace designs

• Less heat stress on the igniter component

• Can be more tolerant of minor voltage fluctuations

But Spark Ignition Has Very Different Failure Patterns

Instead of burning out like an HSI, spark systems mostly fail due to inability to create or sense the flame properly.

Most Common Spark Ignition Failures

1. Dirty or Misaligned Spark Electrode

Because spark igniters sit close to the flame, they can get dirty or corroded—common in dusty areas like the Wiregrass, especially in older homes or near farms.

A dirty electrode can prevent the spark from jumping properly.

2. Poor Grounding

Spark igniters require a clean electrical path.

Loose screws, rusted furnace housing, or older equipment can interrupt grounding.

3. Faulty Flame Sensor

Many spark systems rely heavily on the flame sensor to verify that the flame actually lit.

If the flame sensor is dirty or broken, the furnace will shut down instantly as a safety feature.

4. Weak Spark Module

The module that controls the spark can weaken over time.

Homeowners often describe this as “my heater keeps clicking but never starts.”

HSI vs. Spark: Which System Does Your Wiregrass Home Have?

If you’re not sure which ignition system your furnace uses, here are some quick clues:

You Likely Have HSI If:

• Your system is newer (2003–present)

• You don’t hear clicking noises before the blower starts

• Your manual mentions “hot surface ignition”

You Likely Have Spark Ignition If:

• Your furnace is older or original to the home

• You hear fast clicking during startup

• You have a manufactured-home or mobile-home unit

Eco Heating & Cooling can quickly identify your system type and diagnose failures during a service visit.

Common Symptoms of Ignition System Problems

Homeowners in Dothan, Headland, and Enterprise often call us with the same symptoms:

✔ Heater won’t turn on

✔ Furnace tries to start but shuts off

✔ A burning smell or strong gas smell

✔ Repeated clicking or repeated cycling

✔ Cold air blowing instead of heat

✔ Error light blinking on the furnace

If you notice any of these, shut the system off and call a professional.

An ignition failure may seem small, but ignoring it can lead to bigger and more expensive issues.

Why Ignition Problems Are So Common in the Wiregrass

Dothan and the surrounding areas have several conditions that stress ignition components:

• High humidity

• Dust and sand

• Older home construction

• Voltage fluctuations in rural areas

• Frequent heating/cooling cycles during fall and spring

These factors contribute to faster igniter wear, dirty electrodes, and flame sensor issues.

How Eco Heating & Cooling Protects Your Heating System

Our trained technicians understand the unique demands of the Wiregrass climate. During a heating tune-up, we:

✔ Inspect and clean ignition components

✔ Test spark or HSI operation

✔ Clean the flame sensor

✔ Check voltage to the furnace

✔ Verify gas pressure

✔ Confirm safety limits

✔ Evaluate the control board

✔ Look for cracks or weak spots in the igniter

Catching these issues early prevents the dreaded “no heat” call at night or on a cold weekend.

And yes—we offer 24/7 emergency heating repair anywhere in the Wiregrass.

When to Replace an Igniter vs. Repair the Furnace

Igniters themselves are usually inexpensive compared to major furnace components.

In most Dothan-area homes, replacing a bad HSI or spark component is quick and cost-effective.

However, ignition problems that keep happening may point to:

• A failing control board

• A cracked heat exchanger

• Incorrect gas pressure

• Poor installation in the past

• Age of the furnace (15+ years)

If repeated failures occur, Eco Heating & Cooling can help you determine whether simple repairs or a full system replacement makes the most financial sense.

Final Thoughts: Don’t Ignore Ignition Problems

A faulty ignition system is one of the most common reasons homeowners experience heating breakdowns in the Wiregrass area. Whether your furnace uses HSI or spark ignition, the key is early diagnosis and proper maintenance.

If your heater is struggling to start, shutting off, or blowing cold air, Eco Heating & Cooling is here to help.

We proudly serve Dothan, Headland, Ozark, Enterprise, Daleville, Cottonwood, Kinsey, Taylor, and all surrounding Wiregrass communities.