Finding an F99 error code flashing on your GE dishwasher? This pesky code indicates an issue with your appliance achieving the proper 120°F wash temperature. Before calling the repair shop, try some DIY troubleshooting steps like checking the inlet water temperature, testing the thermistor sensor, and inspecting the heating elements.
With some basic tools and safety precautions, you can often track down the culprit causing the F99 code yourself. Read on to learn what’s behind this temperature-related error and how to systematically diagnose the problem in your GE dishwasher.
What Does the F99 Error Code Mean?
The F99 error code on your GE dishwasher indicates that the minimum wash temperature of 120°F (49°C) was not achieved in 3 out of the past 5 wash cycles. Let’s break this down a bit:
Minimum Wash Temperature Not Achieved
For proper cleaning and sanitization, your dishwasher needs to heat the wash water to at least 120°F during the main wash cycle. If the water doesn’t get hot enough, dishes may not get fully clean and sanitized.
Have you ever run a dishwasher cycle only to find your dishes still look a bit grimy or have food residue stuck on? That’s likely because the wash water didn’t get hot enough to properly clean and dissolve everything.
Control Board Monitors Wash Temperature
Inside your dishwasher, there is an electronic control board that monitors the temperature of the wash water using a thermistor (more on that in a bit). The control board keeps track of the past 5 wash cycles and their temperatures.
If the minimum 120°F temperature wasn’t reached in 3 or more of those 5 cycles, it triggers the F99 fault code as a warning that something needs attention.
Thermistor Changes Resistance
A thermistor is a humble little electronic component that changes its electrical resistance based on temperature. As the water gets hotter, the thermistor’s resistance changes in a predictable way.
The control board uses this changing resistance to calculate the precise temperature of the wash water at any given time during the cycle. Pretty clever, right?
| Cool Fact: Thermistors are used in all sorts of applications – from industrial equipment to smartphone batteries – anywhere precise temperature monitoring is needed!
Have you ever experienced the F99 error on your GE dishwasher? Did understanding what it means help shed some light on the situation? Let’s move on to the troubleshooting steps to resolve this pesky code in the next section!
Safety First! Important Precautions
Before attempting any repairs or maintenance on your dishwasher, it’s crucial to prioritize safety. Dealing with electrical appliances and heated components can be risky if not done properly. Let’s go over some essential precautions to keep you out of harm’s way:
Power Off and Unplug the Appliance
The very first step is to completely disconnect your dishwasher from its power source. Locate the circuit breaker that powers the dishwasher and switch it to the “Off” position. You can double-check by trying to turn on the dishwasher – no lights or sounds should come on.
Next, physically unplug the dishwasher from the electrical outlet. This ensures there is no chance of getting shocked while working on the unit.
Turn Off the Water Supply
Water and electricity don’t mix well, so you’ll want to shut off the water supply line that feeds into your dishwasher. There is usually a dedicated shut-off valve located underneath the sink or nearby. Turn it clockwise all the way to stop any water flow.
It’s also a good idea to have some old towels or rags handy in case you need to mop up any residual water inside the dishwasher tub.
Allow the Appliance to Cool Down
If you’ve just run a cycle, parts of the dishwasher like the heating element and interior tub could still be extremely hot. Let the unit cool down completely before sticking your hands inside to avoid burns.
An easy way to check if it’s cool enough is to carefully place the back of your hand near the air vent – it should feel room temperature.
Work in a Well-Lit, Clutter-Free Area
Good lighting and a clear workspace are crucial for safe dishwasher repairs. Position a bright lamp or work light directly over the area you’ll be accessing. Move any obstructions, tools, or household items away from the area to avoid tripping hazards.
Wear Proper Safety Gear
Depending on the repair, you may want to wear insulated work gloves to protect your hands from sharp edges or heated components. Safety glasses can prevent debris from getting in your eyes. A dust mask is also a good idea if you’ll be dealing with insulation or other particulates.
Step-by-Step: Troubleshooting the F99 Code
Now that we’ve covered the safety basics, let’s roll up our sleeves and dive into the actual troubleshooting process for that stubborn F99 error code on your GE dishwasher. We’ll take it one step at a time:
Step 1: Enter Service Mode
To properly diagnose the issue, we need to put the dishwasher into a special service mode that allows testing individual components. Here’s how:
- Locate the “Heated Dry” and “Delicate” buttons on the control panel
- Press and hold both of those buttons down simultaneously
- Keep holding until the dishwasher enters service mode (indicated by lights blinking or beeping)
- Once in service mode, you can manually activate and test different parts of the cycle
Putting it into service mode is like getting your dishwasher to give you a behind-the-scenes tour and let you poke around under the hood.
Step 2: Check the Inlet Water Temperature
One potential cause of the F99 code is if the incoming water supply isn’t hot enough to begin with. We can check this easily:
- Get a digital food thermometer (or any thermometer that measures up to 140°F)
- Remove the inlet water supply hose from the valve and let some water flow into a cup
- Immediately take the temperature reading of the water in the cup
For proper dishwasher performance, that inlet water should be between 120-140°F. If it’s colder than that range, you may need to adjust your home’s hot water heater.
Step 3: Inspect the Thermistor
The thermistor is the little sensor that monitors the actual wash water temperature inside the tub. Let’s make sure it’s working properly:
- Locate the thermistor on the exterior wall of the dishwasher tub (check your manual if unsure)
- Disconnect the thermistor wires and use a multimeter to test the resistance
- Compare the reading to the resistance value for 120°F in the thermistor resistance chart
If the reading is way off from what it should be at 120°F, the thermistor likely needs replacement. A faulty one can definitely cause the F99 code.
Step 4: Test the Heater Assembly
At the heart of heating the wash water is the heater assembly itself. Here’s how to give it a checkup:
- GE uses a dual-wattage Calrod heater – locate it mounted to the dishwasher tub
- In service mode, initiate just the circulation cycle (no heat yet)
- Use your digital thermometer to monitor the water temperature
- Then turn on the heater and watch for the temp to rise steadily
If the temperature doesn’t increase at all once the heater is activated, the heater assembly may have failed and need replacement. You can also check for proper voltage going to it from the control board.
Step 5: Check the Tub Thermostat
In addition to the thermistor, there is also a high-temp thermostat attached to the tub. This one acts as an emergency shutoff if the water gets dangerously hot:
- Locate the tub thermostat on the outside wall of the tub
- Disconnect the wires and use your multimeter to test for continuity
- It should show a closed circuit unless an unsafe temperature was detected
If the tub thermostat is stuck open or giving abnormal readings, it may need to be resetor replaced to prevent the F99 code.
Step 6: Test and Reset
After inspecting and/or replacing any faulty components, it’s time for a final test:
- Run a Quick Cycle or Rinse cycle to verify the heating components are functional
- Use your thermometer again to confirm at least 120°F is reached
- The dishwasher control should automatically reset and clear the F99 code
And there you have it! By methodically going through each potential culprit, you can get to the bottom of what’s causing that pesky F99 error.
Conclusion
Dealing with error codes on household appliances can be frustrating, but with the right knowledge and approach, you can often resolve issues yourself. The F99 code on GE dishwashers specifically indicates that the minimum wash temperature of 120°F was not achieved in 3 out of the last 5 wash cycles.
This error commonly results from issues with the water heating components or temperature monitoring systems inside the dishwasher. By following the systematic troubleshooting steps outlined earlier, you can pinpoint and address the root cause.
Fixing appliances yourself not only saves money on repair costs but also gives a sense of accomplishment. However, it’s perfectly okay if you don’t feel comfortable diving into the internals of your dishwasher. Requesting professional service is sometimes the wisest choice, especially if you’re unsure about working with electrical components or plumbing connections.
No matter which route you take, the key is understanding your appliance and not ignoring error messages. A little proactive maintenance can go a long way in extending the lifespan of your dishwasher and other household workhorses.