Dryer Not Heating: The Tests a Technician Runs, Gas and Electric

A dryer that tumbles and blows cold air is the most common dryer call we take, and it is also the one most often fixed wrong. There are about eight parts that can stop the heat, and a technician with a meter usually finds the bad one in twenty minutes. Below are the tests we run on a service call, in the order we run them, with the readings we expect. They are written the way we train new technicians, so they assume you already have a meter and the wiring diagram in hand.

One thing holds for every brand. The part that failed almost always failed for a reason, and in South Florida the reason is usually a vent that stopped moving air. Replace a thermal fuse and leave the vent alone, and the new fuse goes the same way within months.

What a technician brings to this call

A no-heat call is a meter job. The minimum kit:

• A digital multimeter rated CAT III for 300 V or more, with probes that are not cracked. Cheap meters with worn leads give false open readings, and on this call a false open sends you after the wrong part.
• A non-contact voltage tester, to confirm a circuit is dead before touching it.
• A manometer that reads in inches of water column, for the vent test.
• 1/4″ and 5/16″ nut drivers, Torx T20 and T25, a flat putty knife for the top-panel clips on Whirlpool-built models.
• For gas dryers: leak-detection solution, a wrench for the flex connector, and the tech sheet for that model.

Find the tech sheet and read the wiring diagram first

Every dryer ships with a tech sheet: a folded paper with the wiring diagram, component resistances and the service-mode button sequence. On Whirlpool, Maytag and Kenmore models built by Whirlpool it is usually tucked inside the control console or behind the toe panel. On Samsung and LG it is often taped inside the back of the control panel or under the top. If it is missing, the model number on the door-frame sticker gets you the PDF from the parts distributor.

Read the heat circuit before measuring anything. On a typical Whirlpool-built electric dryer, current leaves L1, passes through the timer or control, the cycling thermostat, the high-limit thermostat, the thermal cut-off and the heating element, then returns to L2 through the motor’s centrifugal switch. Each of those is in series. One open part anywhere in that chain kills the heat, and the motor keeps turning because it is on a separate path. Samsung and LG electronic dryers put a relay on the main board in that chain and add a thermistor the board reads. Gas dryers replace the element with an igniter, a flame sensor and a gas valve, but the thermostats and fuses are the same idea.

The diagram is how you know which part to test next. Without it you are guessing, and guessing on this circuit is how people end up buying four parts for a dryer that needed one.

Step 1: confirm the dryer is getting 240 volts

This is the test most people skip, and it explains a lot of “no heat” calls. An electric dryer’s motor runs on 120 volts (one leg to neutral). The element needs both legs, 240 volts across L1 and L2. If one leg of the double breaker trips, or one blade of the plug is burned, the drum turns and the air stays cold.

With the dryer plugged in and the terminal-block cover removed at the back, a technician reads:

The 208-volt case is worth knowing in South Florida. A 5,400-watt element is roughly 10.7 ohms. At 240 volts it makes about 5,400 watts; at 208 volts the same element makes about 4,000 watts. Nothing is broken, the dryer just dries slower, and no part swap fixes it.

While the cover is off, look at the terminal screws and the cord. Brown or melted plastic around a terminal means a loose connection that overheated. That terminal block and the cord get replaced, not tightened and reused.

Step 2: electric dryer, test the heat circuit with the power off

Unplug the dryer. Confirm it is dead with the non-contact tester at the terminal block, because a dryer on a mislabeled breaker is still live. Then pull a wire off each part before measuring it, so the meter is not reading through the rest of the circuit. Readings are at room temperature.

Which part blew tells you different things. A thermal fuse on the blower housing of a Whirlpool-built dryer sits in the motor circuit, so when it opens the dryer will not start at all. On most Samsung and many LG models the fuse is in the heat circuit, so the drum turns and nothing heats. The thermal cut-off on Whirlpool-built electrics opens only when the element housing overheats, and it is sold as a kit with the high-limit for a reason: if the cut-off blew, the high-limit is suspect too.

A good reading does not clear a part. Thermostats open at a set temperature, and a worn one can pass the cold test and open far too early once warm. An element can read a clean 10.7 Ω and still touch the heater box when it expands, which trips nothing and heats nothing. And on Whirlpool-built electrics the motor’s centrifugal switch closes the heat circuit only once the motor is up to speed. A tired switch gives every symptom of a dead element with a perfect element in place. Testing it means reading across the switch contacts with the motor running, which is back to live work.

The test sequence also has a trap: never bridge a thermal fuse or a cut-off “just to see if it heats.” Those parts are the only thing between an overheating cabinet and a lint fire, and a jumper wire leaves nothing to stop it.

Step 3: gas dryer, the ignition chain

A gas dryer heats in a sequence. With the burner cold, the flame sensor (Whirlpool calls it a radiant sensor) is closed and passes current to the igniter. The igniter glows. When the flame sensor sees enough heat it opens, which shifts current to the gas valve coils. The coils open the valve, gas hits the glowing igniter, and the burner lights. If any link fails there is no flame.

The first diagnostic step is to watch the burner through the sight hole with the dryer running. What you see narrows it down before you touch a meter:

With the dryer unplugged and the gas supply valve closed, these are the readings on the common Whirlpool and Maytag gas valve (the two-coil kit sold as 279834):

GE, Samsung and LG gas valves use the same two-coil principle, but the resistances vary by valve maker, so the numbers come from that model’s tech sheet. The coil readings also share the thermostat problem: coils that measure fine cold can still drop out once they heat up. That fault shows up as the ten-minutes-then-cold pattern, and it is confirmed by watching the burner, not by the meter.

The silicon carbide igniter is brittle. Touching the glowing element, or even the cold one with oily fingers, shortens its life. Mounting it slightly out of position puts it outside the gas stream, and the burner fails to light even with a new part.

Step 4: measure the vent, because it caused the failure

Whatever part failed, the vent decides whether the repair holds. Heat that cannot leave the dryer is what opens fuses, cooks high-limits and burns out elements early. Looking at the duct does not tell you much. Measuring it does.

A technician puts a manometer probe into the exhaust a few inches behind the dryer outlet, runs the dryer on air-only, and reads the back pressure in inches of water column. Manufacturers’ installation sheets set the limit; most want it under roughly 0.6 to 0.8 inches. Readings near or above 1.0 mean the dryer is pushing against a blocked or overlong run. The test hole gets sealed with foil tape afterward, never left open.

The building code puts a number on the run itself. The International Residential Code allows 35 feet of 4-inch rigid metal duct, minus 5 feet for every 90-degree elbow and 2.5 feet for every 45. A condo dryer that vents 25 feet across a ceiling with three elbows is already at 40 equivalent feet, over the limit before any lint builds up. Add a roof cap whose flap has rusted half shut in the salt air, or a foil accordion transition duct crushed behind the machine, and the dryer is cooking itself.

Some dryers tell you. LG’s Flow Sense shows d80, d90 or d95 when the duct is roughly 80, 90 or 95 percent restricted, and many Whirlpool-built models light a Check Vent indicator. Other brands say nothing until the fuse goes.

Error codes that point at the heat circuit

Codes help, but they name a circuit, not a part. Most electronic dryers store recent codes and show them only in service mode, and the button sequence to get there is printed on the tech sheet.

A thermistor code with a good thermistor sends you to the harness and the board connector. On electronic dryers the heat relay on the main board can also fail with every sensor reading normal, and that board is usually the last part people suspect.

Reset, reassemble, and test under load

Electronic dryers sometimes need a power reset after a fault: breaker off for a full minute, then on. That clears a latched code; it does not fix the cause, and a dryer that throws the same code a cycle later still has the fault.

Reassembly is where a correct repair turns into a second call:

• Terminal block screws go back snug to the torque on the installation sheet; Whirlpool’s sheet calls for about 20 to 25 inch-pounds. A loose terminal arcs and overheats; an overtightened one cracks the block.
• On a four-wire cord the bonding strap between neutral and the cabinet comes off. On a three-wire cord it stays. Getting this wrong puts current on the cabinet.
• Any push-on connector that is discolored gets replaced along with the part it connects to. A loose connector is what burned the old terminal.
• Element mounting screws and heater-box insulators go back in their original positions so the coil cannot touch the box.
• On gas dryers: pipe sealant only on tapered pipe threads, never on flare fittings; flare joints seal metal to metal. Then the leak test.
• Drum seals seated, belt routed around the idler the right way, front panel clips engaged, ground wires back on.

The test that matters is a full timed cycle on high heat with a load, while watching the element or burner cycle. A dryer that heats and never cycles off is the dangerous case: the operating thermostat is not opening, and the high-limit is the only thing left. On our calls the last step is an airflow reading at the outlet, and the before and after numbers go on the invoice.

What our technician does on a no-heat call, and what it costs

Power at the terminal block, the heat circuit part by part against the tech sheet, the vent pressure, then the repair and a full test cycle. Typical South Florida prices with labor:

• Thermal fuse or thermostat: $120 to $220
• Heating element, electric: $170 to $330
• Igniter, flame sensor or valve coils, gas: $150 to $300
• Vent cleaning to the exterior: $140 to $320, less when bundled with the repair
• Foil transition duct replaced with metal: $80 to $160

We repair every dryer brand across Miami-Dade, Broward and Palm Beach, seven days a week. The service call is $59 and it is credited to the repair when you go ahead, and most no-heat dryers are fixed the same day on the first visit. Call (754) 345-4515, or see dryer repair and dryer vent cleaning. Brand pages: LG, Samsung, Whirlpool, GE, Maytag. If the dryer is old and you are weighing a new one, read repair or replace a dryer first.

Questions owners ask