3/12/21
KitchenAid Dishwasher KUDS30IXBL Thermal Fuse
Objective
To convey solutions and information related to the thermal fuse problems that seems to be chronic to KitchenAid (Whirlpool) dishwashers and other manufacturers.
KitchenAid Dishwasher repair blogs and forums have many pages of incidents. I post this report in the hopes that it will be picked up and disseminated and help many KitchenAid dishwasher owners and well as other makes.
History
I purchased a KitchenAid (Whirlpool) Dishwasher Model KUDS30IXBL in September 2011.
After 4 months it died, nothing worked. The repairman replaced the thermostatic fuse. About 4 months later it died again, same problem, repairman replaced the fuse. Another 4 months and it failed for the third time. Repairman said the spade terminals on the fuse were loose and a new wiring harness was needed, but he replaced the fuse.
At this point, being a mechanical engineer, I decided to take matters into my own hands, so I crimped the fuse spade terminals which were so loose they almost slid off by themselves. The dishwasher worked fine until the Fall of 2020 when indicating lights started to work erratically requiring resetting of the circuit breaker. After a few weeks of this it died completely.
I replaced the 4 connectors (on a single plug) at the lower left of the control module with proper spade connectors. The connectors were an unusual design and not standard spade connectors. This worked perfectly for a few weeks, then it died again.
The thermal fuse circuit was open and had to be replaced, but I did a modification to the design as you will see below.
The Problem
I have read lots of threads here and people are replacing the control module, fuses, thermostats, and wiring harnesses. Some comments also allude to house power as the problem or to “baby” the dishwasher as a solution.
Here is what I have determined:
The control module IS NOT the problem.
The thermostat IS NOT the problem.
The wiring harness IS NOT the problem.
The house wiring IS NOT the problem.
The thermostatic fuse IS the problem. (not the fuse itself, but the system design)
The Fix
The fix is simple, safe, and easy to do. The fix is 100% reliable.
No need to “baby” the dishwasher by running without heated dry or sticking to normal cycles.
(see “Solution - How to Fix” section)
Background
Why is there a thermal fuse anyhow? The purpose of the fuse is to protect against the thermostat sticking closed and causing an overheated dishwasher resulting in melted components or even a fire.
The thermostat is located on the bottom of the metal pan on the outside at the front. The thermostat opens and closes to turn the heating coil on and off.
If one were to jumper out the thermostatic fuse the dishwasher would work fine, but it would not be safe. DO NOT install a jumper.
How the Fuse Works
Inside the fuse is a small thin round bi-metallic plate, a little smaller than a dime. Each side of the plate is a different material, each with a different thermal expansion rate. The plate is concave on one side, convex on the other. When the fuse reaches the trip temperature the plate convex-concave reverses, operating a small pin and breaking the electrical circuit.
Fuse Tripping
The fuse gets heat from two sources, from the ambient air around the fuse and from heat generated by electric current passing through the fuse. The intention is for ambient air to do the tripping and not the current flow (amps).
The problem is that the primary source of heat is from the current flow and not the ambient temperature.
Electrical Design Issue
Estimated current draw:
Heater: 7 amp
Motor: 2 amp (in-rush current could be 50% to 100% more)
Solenoid Valve: 0.5 amp
Control Module: 0.2 amp
All electricity for the dishwasher flows through the fuse. The current flow varies as different items start and stop in the programmed sequences.
Ideally, the current flow through the fuse would be small and steady.
What Happens
Electrical contact internal to the fuse and other connections degrade over time due to oxidation, resulting in more resistance in the circuit. Normally, in most electrical circuits, this would not be a problem, but in this dishwasher there is minimal reserve margin.
This contact degradation, resulting in more electrical resistance, causes more heat generation within the thermal fuse. This explains why the fuse failed every few months (like clockwork for me).
Solution - How to Fix
The solution is to reduce current flow (amps) through the fuse. There are two ways to accomplish this. I used method 2 on my unit.
Method 1:
Install a relay in the circuit so that the only current going through the fuse is the small amount needed energize the relay coil (less than 1/100 amp) vs the 8-10 amps with all current going through the fuse.
Wire the NO (normally open in shelf condition) relay contacts in place of the fuse. Wire the fuse and the relay coil in series between the hot (black) and neutral (white) 120 volt power wires.
Note that the relay will always be energized holding the NO contacts closed.
Use a standard SPDT ice cube style relay with spade connectors, 15 amp contact rating and 120 volt coil. Use 14 gage stranded wire similar to the existing wiring.
Mount the relay inside the door to the left of the control module.
Method 2:
Wire a second thermal fuse in parallel with the existing fuse. The current draw will then be 50% through each fuse. The 8-10 amp now will be 4-5 amps per fuse.
Use two sections of 14 gage stranded wire similar to the existing wiring and splice one each into the two black leads beneath the control module. These are the leads going into the control module directly to the fuse. Install spade connectors onto the free ends of the two new wire sections.
Install the new thermal fuse onto one of the two spade connector.
Pass the fuse through a 4” long piece of 1” PVC tube and install the second spade connector to the fuse. Slide the fuse into the middle of the PVC tube.
Mount the PVC tube just to the left of the control panel, above the fiberglass insulation, and cable tie the tube through the existing unused slot just behind the door handle.
Replacement Thermal Fuse Part
There is no need to buy a manufacturer’s OEM part costing as much as $30. I purchased NTE Electronics Disc Thermostats from Galco.
http://www.galco.com/buy...TE-DTO190?type=ac_searchCost is $2.78 each so I bought 6. These are identical in physical size to the existing, but are 190 oF opening and 160 oF to reset. The existing ones are one-shot meaning once they open they are no good. The NTE/Galco part is rated 15 amps.
The reset feature is a big advantage. If the fuse trips, then the dishwasher goes dark for some minutes until the fuse cools to 160 F, then the dishwasher flashes blue light until the start button is pressed. This is your indication that something is wrong and needs attention.
Result
With either Method 1 or Method 2, the fuse most likely will never fail again because the current (amps) through the fuse is significantly reduced. Dishes will be cleaner than ever due to more amps being deliver to the heater.
Summary
My KitchenAid Model KUDS30IXBL, in my opinion, has “good bones”. The motor, pump, and heater all seem to be of great quality. The unit runs very quietly and there has never been a leak.
However, there are two weak spots in the design. First is the thermal fuse discussed above. Second is the upper rack wheels which fall off after the plastic wheel axles age and break. I have redesigned and repaired both of these issues on my unit.
Now I feel that my dishwasher is robust and could work for another 10 years. It is already over 9 years old. The shame is that the customers have to redesign and fix their own machines when this should be done at the factory Engineering Department.
Since resolving the thermal fuse issue, the dishes come out sparkling clean even on normal cycle. The reason is very simple – hot water. Thermal fuse degradation results in excess resistance limiting the flow of current (power) to the heater, resulting in water not getting hot enough. The golden rule is “Hot Water = Clean Dishes”.
