Charlotte Plumber DIY Series: How to Fix a Broken Dishwasher - Part I

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Learn How to Fix Dishwashers

Repairing a dishwasher yourself is not challenging and can save you money too. Here are some parts of the dishwasher that could be the source of your problem, and brief descriptions as to how to fix dishwashers in general.  This DIY project has been broken down into two articles since there are so many possibilities. Be sure to check out Part II of this series if you don't find the problem and solution in this article!

Option One: piston and nut assembly

There are some dishwashers that use a check valve as part of the drain sump. Inside that check valve, there is a piston and nut assembly. The piston and nut assembly may be the problem if your dishwasher is not draining correctly.

At the bottom of the tub beneath the sump cover, is where the piston and nut assembly is located. To retrieve the assembly, you must remove four screws.

Afterwards, the assembly should be able to move up and down freely, and when the piston is in the down position, it should create a tight seal. Please note that if it is not creating a complete, tight seal, the dishwasher will not pump out the water completely and the piston and nut assembly will need to be replaced.

It would also be beneficial to examine the body valve gasket that is over the piston and nut assembly to make sure it still fits properly. If it is damaged or worn, replace it.

Option Two: drain pump and motor

No matter the model of the dishwasher, they all have a method to drain water. Some models have a separate drain pump, some models utilize the main circulating pump along with a drain solenoid and diverter valve or flapper, or most models have a single motor driven pump with two separate compartments, one for circulation and one for drain (each with its own impeller).

With the first type of models listed, the ones that use a separate drain pump, you should inspect if there is any obstruction or damage to the input and output of the pump as well as confirm that power is getting to the pump motor during the drain portion of the cycle. If both are fine, then the problem is with the pump and motor assembly, which you should replace.

With the second type of models listed, the ones with a drain flapper and solenoid, once again, inspect any obstructions and confirm that the solenoid is getting powered and that there is continuity. To make these examinations, use a multi-meter. Make sure that the linkage operating the flapper or diverter is freely moving and replace any parts that are faulty.

With the last and most common type of models listed, the ones that have a two section pump, the drain impeller may be at fault. Firstly, confirm that the motor is running in the proper direction, and if the motor is not running, check for power at the terminals on the motor.

You should inspect door switches, timer or electronic control as a possible cause if voltage is not present. However, the motor windings could be open if the proper voltage is present.

If the motor is humming, it is probable the problem is that the drain impeller is jammed or that the motor is seized. The motor or the motor and pump assembly will need to be replaced if the motor is seized. Once again, a multi-meter can make the electrical checks.

To deduce if the impeller is the problem with the dishwasher, it is necessary to disassemble the pump. Normally, the drain compartment is located beneath the circulating compartment.

First, take off the lower rack, spray arm, pump cover, and filter assembly to gain access to the drain compartment.

Second, examine the drain impeller for damage and if replacement is required.

Verify that the food chopper is in good condition and not permitting large food particles to clog the drain, and that the chopper and impeller are both turning freely.

Option Three: valve flapper

There are some dishwasher models that use a check valve in the drain outlet. This check valve is what permits water to flow in one direction, but also what prevents the dirty water from re-entering the dishwasher. Typically, the valve is a rubber flapper located on the outlet port of the drain pump or housing. The check valve is most likely the problem if the drain house has a restriction or damage on it or if the waster water is re-entering the dishwasher tub.

During the drain portion of the cycle, the flapper valve should fully open. However, during the wash or circulation portion of the cycle, the opening to the pump outlet should be closed. The check valve is the problem and should be replaced if there are no foreign objects restricting this action.

Didn't Find Your Problem Yet?

This DIY project has been broken down into two articles since there are so many possibilities. Be sure to check out Part II of this series if you don't find the problem and solution in this article!

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Article Summary

Quick question & answer: Why is my dishwasher broken?

The piston and nut assembly, drain pump and motor, or valve flapper could be the reason for your broken dishwasher. If your dishwasher is not draining correctly, it may be the piston and nut assembly or the drain pump and motor. A malfunctioning valve flapper would cause waste water to enter the dishwasher.

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