How to Diagnose a Dryer That Won't Heat

The drum turns. The dryer runs. But the clothes come out cold and wet. This is one of the most common service calls you'll get, and the good news is the diagnosis is usually straightforward — there's a short list of parts that cause 90% of no-heat conditions.

The diagnosis splits based on whether it's electric or gas. The airflow and lint path are the same, but the heat source is completely different.

First: Rule Out the Simple Stuff

Before you pull any panels:

Check the vent. A clogged dryer vent is the most common cause of poor drying performance. If the exhaust vent is blocked, the dryer can't expel moisture. The thermal fuse or high-limit thermostat will trip from excessive heat buildup, killing the heat source entirely. Disconnect the vent from the back of the dryer and run a cycle. If it heats up fine with the vent disconnected, the vent is your problem — not the dryer.

Check the breaker. Electric dryers run on a 240V circuit with a double-pole breaker. If one leg of the breaker trips but the other doesn't, the dryer gets 120V — enough to run the motor and controls, but not enough to power the heating element. The dryer tumbles but doesn't heat. Check both sides of the breaker. Reset it or swap it if one side is tripped.

Check the settings. It sounds obvious, but verify the customer hasn't accidentally set it to "air fluff" or "no heat." It happens more often than anyone admits.

Electric Dryer: The Heat Circuit

An electric dryer's heat circuit is a series loop. Power flows from L1 through a chain of safety devices and the heating element, then back to L2. If any one component in that chain opens, the element gets no power.

The chain, in order:

Thermal fuse → High-limit thermostat → Cycling thermostat → Heating element

Each one can be tested with a continuity check. Unplug the dryer, access the back panel (most dryers) or front panel (some GE models), and test each component in sequence.

Thermal Fuse

This is the first thing to check and the most common failure. The thermal fuse is a one-shot safety device — once it blows, it stays open and the dryer won't heat until you replace it. It's typically mounted on the blower housing or exhaust duct inside the dryer.

Test: unplug the dryer, disconnect one wire from the fuse, check continuity. Should read 0Ω (closed). If it reads OL (open), it's blown.

Critical point: the thermal fuse doesn't blow for no reason. If you replace it without fixing the root cause, it'll blow again. The root cause is almost always a restricted vent or a failed cycling thermostat that let the dryer overheat. Always check the vent after replacing a thermal fuse.

High-Limit Thermostat

This is another safety device, usually mounted on the heater housing. It opens if the temperature exceeds a set limit (usually around 250°F). Unlike the thermal fuse, some high-limit thermostats are resettable — but most in modern dryers are one-shot like the thermal fuse.

Test the same way: continuity should be 0Ω at room temperature. OL means it's open and needs replacement.

Cycling Thermostat

This thermostat controls the normal operating temperature. It cycles the heating element on and off to maintain the target temperature. When it fails, it can either stay open (no heat) or stay closed (continuous heat, which then blows the thermal fuse or high-limit).

Test continuity at room temperature — it should be closed (0Ω). If it's open at room temperature, it's failed.

Heating Element

The element itself is a coiled resistance wire inside a metal housing. Over time, the wire can break from thermal cycling. When it breaks, the circuit opens and there's no heat.

Test resistance between the two terminals. A good element typically reads 8-25Ω depending on the model. OL means the wire is broken. Also test each terminal to the element housing (ground) — should be OL. If you get continuity to ground, the element is shorted and will trip the breaker.

Gas Dryer: The Ignition System

Gas dryers use a different heat system: a gas valve, an igniter, flame sensor coils, and a burner. The failure sequence is different from electric.

The Normal Gas Ignition Sequence

Understanding the normal sequence helps you figure out where it's failing:

1. Control board sends power to the igniter.

2. Igniter glows bright orange (draws 3-4 amps).

3. When the igniter reaches full temperature, its resistance drops, which increases current flow.

4. The increased current activates the gas valve coils (flame sensor coils).

5. Gas valve opens, gas flows to the burner.

6. Gas ignites from the glowing igniter.

7. Igniter shuts off (flame sensor detects the flame).

If any step fails, you get no heat.

Gas Valve Coils (Most Common Gas Dryer Failure)

The gas valve has two or three solenoid coils that open the valve. These coils are the most common failure on gas dryers — and they have a specific failure pattern. They work fine when cold but fail when hot. So the dryer heats up on the first cycle, then stops heating on subsequent cycles. The customer says "it worked fine the first time but now it won't heat."

To confirm: watch the ignition sequence. If the igniter glows bright orange, then shuts off, but no gas flows (no flame), the coils aren't opening the valve. Replace the coil set. Always replace all coils together — they come as a kit.

Igniter

If the igniter doesn't glow at all during the heating cycle, it's either failed or not getting power. Check power at the igniter harness connector first. If you have voltage but no glow, the igniter is bad. If no voltage, trace back to the control board — the flame sensor circuit or timer may not be calling for heat.

If the igniter glows weakly (dim orange, not bright), it might not be reaching the temperature needed to trigger the gas valve coils. Replace it. Igniters are fragile — handle with care, don't touch the element with your fingers (oil from skin creates hot spots that shorten its life).

Thermal Fuse (Gas Dryers Have Them Too)

Same part, same test, same root-cause issue as electric dryers. Gas dryers have a thermal fuse in the exhaust path. If it's blown, the dryer typically won't run at all (on some models) or won't heat (on others). Test continuity, replace if open, check the vent.

The Diagnostic Shortcut

For electric dryers, work the series chain: thermal fuse → high-limit → cycling thermostat → element. Test each for continuity. The first one that reads OL is your failure.

For gas dryers, watch the ignition sequence. That single observation tells you everything:

- Igniter doesn't glow → igniter or power issue

- Igniter glows then shuts off, no flame → gas valve coils

- Igniter glows, gas flows, no ignition → burner alignment or gas supply issue

- Nothing happens at all → thermal fuse, timer, or control board not calling for heat

The service manual for the specific model gives you the exact resistance values, wiring colors, and test points. Generic values get you close. Model-specific values get you certain.

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