Whirlpool Dishwasher Not Drying Dishes — 5 Causes & How to Fix

You unload the dishwasher an hour after the cycle finishes, and the plates are still wet. Not just a little damp — actually dripping. Your Whirlpool WDF520PADM or WDT730PAHZ ran through the entire cycle, made all the right noises, but skipped the most important part: getting your dishes dry.

Here's the thing: when a dishwasher won't dry properly, most people assume it's the heating element. And yeah, that's often the culprit. But there's a less obvious component that fails just as often and costs way less to replace — the high limit thermostat.

This little safety device (part #661566) monitors the temperature during the drying cycle. When it fails, your dishwasher either won't heat at all or shuts off the heat prematurely. Let's walk through what's actually happening inside your machine.

Quick Symptom Check

Before you start pulling panels off, verify you're dealing with a drying issue and not something else:

• Dishes are wet after full cycle completion — especially plastic items that air-dry poorly anyway
• No steam visible when you crack the door open mid-cycle
• Inside walls feel cool to touch right after the wash cycle ends
• Dishes are clean but soaking wet — rules out spray arm or detergent problems
• Rinse aid dispenser is full — low rinse aid makes drying worse but doesn't eliminate heat

If you're checking three or more of these boxes, you've got a heating system problem. Now let's figure out which part gave up.

Cause #1: Failed High Limit Thermostat (Most Likely — 40% of Cases)

The high limit thermostat is a safety cutoff that prevents your dishwasher from overheating. It's a small disc-shaped component mounted directly on or near the heating element. When the temperature exceeds about 180-200°F, it's supposed to temporarily cut power, then reset when things cool down.

Why it fails: Constant thermal cycling wears out the bimetal mechanism inside. After a few years, it either stays open (no heat ever) or gets stuck closed (which can actually damage the control board or element). On Whirlpool, Maytag, and KitchenAid models, this part has a known failure pattern around the 4-6 year mark.

How to test it:

1. Unplug the dishwasher and shut off the breaker — you're working with both water and electricity here
2. Remove the lower front panel (usually 4-6 screws along the bottom edge)
3. Locate the heating element — it's the metal loop at the bottom of the tub
4. The thermostat is a small round component with two wires, mounted with a bracket to the element
5. Disconnect the two wire terminals and test continuity with a multimeter
6. At room temperature, you should read 0 ohms (continuous circuit)
7. If it reads infinite resistance, it's failed open and needs replacement

Difficulty: Easy to moderate. If you can use a screwdriver and a multimeter, you can do this.

Cost: The OEM part 661566 runs about $27.99. Takes 20-30 minutes to replace.

Cause #2: Heating Element Burned Out (35% of Cases)

The heating element itself is basically a big resistor that converts electricity into heat. They don't last forever. Hard water buildup, power surges, or just age can cause them to develop breaks in the heating coil.

How to test it:

1. With the dishwasher still unplugged, locate the element at the tub bottom
2. Trace the wires to the connection point (usually under the tub)
3. Disconnect the wires and test resistance across the element terminals
4. You should read between 15-30 ohms typically (check your model's specs)
5. Infinite resistance = broken element
6. Also test from each terminal to ground (the metal tub) — should read infinite. If it doesn't, the element is grounded out and definitely needs replacement

Visual clue: Sometimes you can see a crack or break in the element coil. If it's blistered, corroded, or obviously damaged, skip the testing.

Cost: Heating elements run $40-$80 depending on the model. Replacement takes about 45 minutes.

Cause #3: Defective Control Board or Timer (15% of Cases)

The control board tells the heating element when to turn on. If the board's relay for the heating circuit fails, the element never gets power — even if the element and thermostat are fine.

How to diagnose: This one's trickier. If you've tested the thermostat and element and both check out, and you're comfortable with a voltmeter, you can check for voltage at the element terminals during the heat cycle. You should see 120V when the heater should be running. No voltage = control board issue.

Honestly? If you're not experienced with appliance electronics, this is where you call a tech. Control boards cost $150-$300, and you don't want to replace it if that's not actually the problem.

Cause #4: Blown Thermal Fuse (5% of Cases)

Some models (especially newer Whirlpool WDT series) have a one-time thermal fuse in the heating circuit. If the dishwasher overheated once — maybe the high limit thermostat failed closed — this fuse blows to prevent a fire.

Once it's blown, it's done. Zero continuity, no reset. You'll find it near the control board or heating element, and it looks like a small ceramic or plastic component with two wires.

Test: Check continuity. Should read 0 ohms. If it's open, replace it (usually $15-$25), but also figure out why it blew or you'll just blow the new one.

Cause #5: Vent or Fan Assembly Issues (5% of Cases)

The heat has to go somewhere. Most dishwashers use a vent and fan system to pull hot, moist air out during the drying cycle. If the vent is clogged or the fan motor quit, the dishes won't dry even if the heating element is working fine.

Quick check: During the drying cycle (if you're getting any heat at all), put your hand near the vent opening — usually at the top of the door or on the front panel. You should feel warm, moist air being actively pushed out. Nothing? Fan or vent problem.

Fan motors run $30-$70. Vent assemblies are cheaper but require more disassembly to access.

When to Call a Pro

Look, I'll be straight with you: if testing the high limit thermostat and heating element didn't solve it, and you're not comfortable working with electrical diagnostics, call someone. Chasing down control board issues or intermittent sensor problems without experience usually means buying parts you don't need.

But the thermostat? That's absolutely a DIY fix if you've ever replaced any appliance part before. It's two screws and two wire connectors. Total cost: under $30 and half an hour of your Saturday.

For models WDF520PADM, WDT730PAHZ, WDT720PADM, and the entire WDF/WDT lineup, the 661566 thermostat is the same part. One fix works across dozens of models.

Frequently Asked Questions

Will running the dishwasher with a bad high limit thermostat damage anything else?

Probably not. If the thermostat failed open (most common), the element just won't heat. Your dishes won't dry, but nothing's getting damaged. If it failed closed — stuck in the "on" position — the element could overheat, but modern dishwashers have backup fuses to prevent fires. That said, don't keep running it once you know there's a problem.

Can I just use the heated dry option to fix this, or adjust settings?

If the heated dry option isn't working, adjusting settings won't help. That's the whole problem — the heating system isn't functioning. Some people try using rinse aid or opening the door after the cycle (which does help dishes air-dry faster), but that's a workaround, not a fix. You're still dealing with a failed component that needs replacement.

How long does a dishwasher high limit thermostat usually last?

Most OEM thermostats last 5-8 years under normal use. Hard water areas see failures sooner because mineral buildup on the heating element causes uneven heating, which stresses the thermostat. If you're replacing it on a 10-year-old dishwasher, don't be surprised if you need to replace the element at the same time — they age together.