How to Walk an Electric Dryer Heat Circuit with a Meter

Why this matters

"Runs but no heat" on an electric dryer is a series circuit with five or six parts in it, and the element is the one people order because it is the one they have heard of. Order it on a dryer whose fault is a centrifugal switch and the dryer still runs cold with a new element in it. A cold resistance walk catches most failures, but not all of them: one part in the circuit is supposed to read open when the dryer is off, and an element with a crack can read fine cold and open hot. So the walk has two halves, cold readings on every part, then one voltage reading across the element while the dryer calls for heat. Together they say which side of the element the fault is on. What to do once the part is found belongs to 'Dryer Heating Fault Repair Standard'; this card is the diagnosis.

240 V, a turning drum, and a hot housing

Dead for every resistance reading. Unplug the dryer, or switch off its double-pole breaker if the cord is out of reach. Prove it dead at the terminal block, L1 to L2, L1 to neutral and L2 to neutral, with a meter checked on a known live source before and after, per NFPA 70E Article 120 (120.5 in the 2021 edition; check the current edition for its number). A dryer circuit can lose one leg at a half-tripped breaker and still carry 120 V on the other, so all three pairs get read, not just one.

The live readings. Two readings in this card are taken live: supply at the terminal block, and voltage across the element while heat is called for. The element test means the drum turning, the blower spinning and 240 V on exposed element terminals with the rear or front panel off. Clip your leads onto the test points with the dryer unplugged, route them out of the way of the belt, pulleys and blower, then plug in, start the cycle on a heat setting, and keep both hands outside the cabinet while it runs. Unplug before you unclip.

Heat. The element housing and the limits stay hot for several minutes after a heat call. Let them cool before you handle anything.

The circuit you are walking

The layout below is a common one; the order of parts differs between makers, and some put a thermal fuse or a thermal cutoff in the same path. The wiring diagram for the model is the authority, and 'How to Read a Wiring Diagram You Have Never Seen' covers working one out.

  series heat path, one common order

  L1 (120 V to N)
   |
  TIMER HEAT CONTACT or BOARD RELAY
   |
  HIGH LIMIT      on heater housing,
   |              opens on overheat
   |
  ELEMENT end A
  ELEMENT end B   240 V across A-B
   |              when heating
   |
  CYCLING THERMOSTAT   on exhaust duct,
   |                   cycles the heat
   |
  MOTOR CENTRIFUGAL SWITCH   closes only
   |                         at speed
   |
  L2 (120 V to N)

The current path runs from L1 through the heat contact, the high limit, the element, the cycling thermostat and the centrifugal switch to L2. Every part must be closed at once for the element to heat. The motor itself runs on 120 V, L1 to neutral, which is why a dryer that has lost L2 tumbles normally and never heats.

The cold walk

Unplugged and proved dead. Pull one wire off each part as you read it, so you read the part and not the circuit around it.

1. High limit. Near zero ohms. OL means it is open, and a high limit that has opened did so for a reason, usually restricted airflow or a grounded element; see related: 'Thermal Fuses, High Limits and Cycling Thermostats in Appliance Heat Circuits' for the device stack and why replacing an open limit without finding the cause brings the dryer straight back.
2. Thermal fuse or thermal cutoff, where this model has one in the heat path. Near zero ohms; OL is open, and the same rule applies about the cause.
3. Cycling thermostat. At room temperature it is closed, near zero ohms. It opens only when warm.
4. Element. Read across its two terminals and compare with the tech sheet. Check it against the rating plate too: resistance is close to the rated voltage squared divided by the rated watts, a check owned by 'Estimating Heater Resistance From the Rating Plate Wattage'. Then read each terminal to the heater housing: OL both ways, or the element coil is touching its housing and the dryer is a shock and trip hazard.
5. Centrifugal switch. Find its heat-circuit terminals on the motor. With the motor stopped, those contacts read OL, and that is correct, because the switch closes only when the motor is spinning. A cold OL here is not a fault and a cold near-zero reading is: a switch welded closed would send heat to an element with no airflow over it.

What the cold walk cannot catch: a centrifugal switch that fails to close when the motor runs, an element that opens only when it heats and expands, and a supply missing one leg. The live half covers those.

The live half

1. Supply first, at the terminal block. Dryer unplugged, clip the leads to L1 and L2, plug in. You want about 240 V L1 to L2, and about 120 V from each of L1 and L2 to neutral. A reading near 120 V L1 to L2, or one leg near zero to neutral, is a supply fault: the breaker, the receptacle or the cord. That is the end of the dryer diagnosis until the supply is right. Unplug.
2. Across the element, calling for heat. Clip the leads to the element's two terminals, dryer unplugged. Plug in, choose a high heat setting, and start the dryer. Hands out of the cabinet. Read the voltage, and if you have a clamp meter, clamp one element lead too.
   • About 240 V across the element and current flowing: the element is heating, and the fault, if there is one, is not in this circuit.
   • About 240 V across the element and no current: both ends are powered and the element is open, most likely a break that opens when hot.
   • About 0 V across the element: one end is not reaching its supply. Go to step 3.
3. Across each device in turn. Reading an element end to neutral does not split the fault: both ends read about 120 V to neutral whichever side is open, because the element connects them. Read across the devices instead. Unplug, clip across one device, plug in, start on heat, read; repeat for the heat contact or relay, the high limit, the cycling thermostat and the centrifugal switch. A closed device reads about 0 V across it. The open one reads about 240 V, because it is the only gap between L1 and L2.

The current a working element draws is close to rated watts divided by line voltage, so a 5,400 W element at 240 V draws about 22.5 A, the figure a clamp meter confirms.

A worked case

An electric dryer, tumbles normally, no heat at all, clothes come out damp and cold after an hour. The rating plate gives a 5,400 W element at 240 V.

Unplugged and proved dead at the terminal block, all three pairs.

Cold walk:

• High limit: 0.2 ohms. Closed.
• Thermal fuse, in this model's heat path: 0.1 ohms. Closed.
• Cycling thermostat, room temperature: 0.1 ohms. Closed.
• Element: 10.9 ohms. From the rating plate, 240 V squared is 57,600, divided by 5,400 W gives 10.7 ohms; 10.9 is within a few percent of that and inside the tech sheet range. Each terminal to housing: OL. Good.
• Centrifugal switch heat contacts, motor stopped: OL. Correct for a stopped motor.

Every cold reading is right, which is exactly the situation where an element gets ordered on habit.

Live: supply at the block reads 241 V L1 to L2, 121 V L1 to neutral, 120 V L2 to neutral. Supply is good.

Across the element, drum turning on high heat: 0 V. Clamp on the element lead: 0 A. One end is not reaching its supply.

Across the cycling thermostat, running on heat: 0 V. Closed, as it should be with the dryer cold. Across the centrifugal switch heat contacts, running on heat: 240 V. The motor is up to speed and the switch has not closed. That is the open device.

On this motor the switch is part of the motor assembly, so the motor is the part, ordered on a reading taken while it was running rather than on a cold OL that every good switch shows. The element stays.

What would have changed the call. If the supply had read 120 V on one leg and near zero on the other, the work is the breaker or receptacle, and the customer is told before a part is quoted. If the element had shown 240 V and 0 A, a new element, and the cause of an element failing, airflow, gets looked at. If the high limit had read OL cold, the next question is why it tripped, starting with the vent; 'Dryer Exhaust Length and Fittings Card' covers what the run should look like.

The finish test

1. Reassemble every panel and reconnect every wire you lifted, comparing against the diagram.
2. Run on high heat for ten minutes with the drum empty. Clamp the element lead through the side panel opening if your model allows, or confirm heat at the exhaust hood outside: hot, moist air moving strongly.
3. Watch it cycle. After a few minutes the cycling thermostat opens and current drops to zero, then returns. A dryer that never cycles off, with good airflow, has a thermostat problem.
4. Stop the dryer mid-heat by opening the door. The motor stops, the centrifugal switch opens, and the heat must drop out with it. Listen for the element relay or watch the clamp go to zero.

Write on the ticket: supply readings, each cold reading, the live reading that found the fault, the part replaced, and the exhaust air confirmed hot at the hood.

References

• See related: Dryer Heating Fault Repair Standard; Thermal Fuses, High Limits and Cycling Thermostats in Appliance Heat Circuits
• See related: Estimating Heater Resistance From the Rating Plate Wattage; How to Read a Wiring Diagram You Have Never Seen
• See related: Dryer Exhaust Length and Fittings Card; 240 Volt Appliance Receptacles and What Each Reads
• NFPA 70E, Standard for Electrical Safety in the Workplace, Article 120, current edition (verifying absence of voltage)
• Manufacturer wiring diagram and tech sheet for the model: heat circuit order and element resistance