For a new sharp microwave user, to handle an automatic microwave, such as a sharp microwave can be difficult at times until you master how the sharp microwave operates.
Having a microwave that turns on by itself randomly or runs briefly before shutting off is really annoying because I have personally face that issue. If your Sharp microwave exhibits this issue, where it only operates for a few seconds before turning off abruptly, there could be several potential causes behind this erratic behavior.
This guide will equip you with the necessary steps to troubleshoot and fix a Sharp microwave that exhibits spontaneous powering on or abrupt shutdowns after a short usage period.
You can effectively address these issues and restore the microwave’s optimal functionality with the guidance provided. We’ll explore common reasons, like faulty door switches, control panel issues, and electrical component problems that could trigger your microwave to turn on randomly or prevent it from running a complete cycle.
Potential Causes
There could be several potential causes behind a Sharp microwave turning on by itself or running briefly before shutting off. Here are some common issues that may be responsible:
- Control Panel and CPU Errors
- When entering instructions into the control panel, power surges or issues can lead to CPU errors, causing the microwave to behave erratically.
- CPU errors are commonly caused by power surges or software problems when entering instructions into the control panel.
- Door Switch Malfunction
- A faulty door switch could be the culprit if the microwave shuts off after a few seconds. Checking the door switches is crucial, especially the uppermost one, as it is in series with the high-voltage transformer.
- A thermistor or Temperature Sensor Failure
- A faulty thermistor or temperature sensor can cause the microwave to shut off prematurely.
- Standard error codes related to thermistor failure include EE6, EE10, and EE16.
- Fan and Blower Issues
- Problems with the two squirrel cage blowers in the back may suggest a possible fan motor switch issue, leading to the microwave shutting off.
- Error code EE0 indicates a fan lock error.
- Magnetron and High Voltage Issues
- Magnetron failure (error codes EE1, EE2, EE3) or a diode failure can prevent the magnetron from heating, causing the microwave to shut off.
- Voltage issues, either too high (EE4) or too low (EE5), can also lead to the microwave turning off prematurely.
- Electrical Component Failures
- A blown line fuse can prevent the microwave from starting.
- Issues with the main control board may cause the microwave to turn on by itself or display malfunctions (error code EE8).
- A damaged waveguide cover can lead to sparking or arcing, forcing the microwave to shut off.
By identifying the root cause, whether it’s a faulty component or an electrical issue, you can take the appropriate steps to troubleshoot and repair your Sharp microwave effectively.
Checking Door Switches
One of the most common reasons a microwave turns on briefly and shuts off is an issue with the door switches. These switches are crucial safety mechanisms preventing the microwave from operating when the door opens. Most microwaves have 3-4 door switches mounted near the door latch. Here’s how you can inspect and test them:
Inspecting the Switch Holder
- Locate the switch holder that houses the door switches.
- Inspect it for any damage or misalignment, as this can prevent the switches from being actuated properly.
- If the switch holder is damaged or misaligned, replace it with a new one.
Testing the Door Switches
- Disconnect the wiring harness leads from the switch terminals.
- Use a multimeter to test each door switch and micro switch for continuity.
Testing a 3-Terminal Door Switch
- Adjust your multimeter to the minimum resistance measurement in ohms.
- Touch the C.O.M. (common) terminal with one probe and the N.O. (normally open) terminal with the other.
- The meter should read infinity (open circuit) when the switch is not pressed.
- When the switch is pressed, the meter should read 0 ohms (closed circuit).
- Repeat the test by touching the C.O.M. terminal and the N.C. (customarily closed) terminal.
- The meter should read 0 ohms when the switch is not pressed.
- The meter should read infinity when the switch is pressed.
- Check the resistance between the N.O. and N.C. terminals, which should read infinity.
- Check the resistance from each terminal to any metal mounting hardware, which should also read infinity.
- Replace any door switch that does not meet the expected results, indicating a defective switch.
Suppose the door switches function correctly, but the microwave shuts off after a few seconds. If such a scenario arises, delving into other plausible reasons contributing to the issue would be advisable. This could include scrutinizing factors like malfunctioning control panels, faulty thermistors, damaged fans, or any electrical components that may have been affected.
Testing the Control Panel
The CPU (central processing unit) inside the microwave controls the cooking program, timer, carousel, and all input from the control panel. If your Sharp microwave is turning on by itself or running briefly before shutting off, there could be an issue with the control panel or CPU. Here are some troubleshooting steps you can take:
Clearing Erroneous Input
- Tap the Stop/Clear button a few times to cancel the current program and clear any erroneous input that may confuse the CPU.
- Re-enter the cooking instructions carefully, ensuring you input the correct settings.
- Press Start/Minute Plus to begin the cook cycle.
Checking for Lockout or Demonstration Mode
- Ensure the CPU is not in lockout mode by pressing Clock, 1, then holding Start for 3 seconds to activate the microwave.
- Press Clock, 0, then hold Stop/Clear for 3 seconds to exit demonstration mode, which prevents the microwave from cooking food.
Resetting the CPU
- Disconnect the microwave from power for 1 minute.
- Plug it back in to reset the CPU if it is scrambled due to a power surge or fault.
If these steps don’t resolve the issue, you may need to inspect the control panel for any physical damage or malfunctioning buttons. In some cases, replacing the control panel or specific components like the rotary knob or buttons may be necessary.
Error Code
Potential Issue
EE1, EE2, EE3
Magnetron failure
EE4
Voltage too high
EE5
Voltage too low
EE6, EE10, EE16
Thermistor failure
EE0
Fan lock error
EE8
The main control board issue
Please pay attention to any error codes displayed on the control panel, as they can indicate specific issues like magnetron failure, voltage problems, thermistor failure, or control board problems, which may require further troubleshooting or component replacement.
Inspecting Electrical Components
To troubleshoot electrical component issues that may be causing your Sharp microwave to turn on by itself or run briefly before shutting off, you’ll need to inspect various components and test them for proper operation. Here are the steps you can follow:
- Access the Internal Components
- Unplug the microwave from the power source.
- Remove the outer casing or metal cover to access the internal components.
- Discharge the High Voltage Capacitor
- Locate the high-voltage capacitor.
- Use a 20K ohm resistor tool to safely discharge the capacitor before proceeding.
- Test the Capacitors
- Check the capacitors for continuity and resistance using a multimeter.
- When tested for continuity, the capacitor should have no reading and a resistance of 180-350 megohms in one direction and 20-50 megohms in the other.
- Test the Microwave Diode
- Check the voltage drop across the microwave diode using a multimeter.
- Test the resistance in both directions. The diode should have a resistance of around 0.1-0.3 ohms between the terminals.
- Inspect the Magnetron
- Visually inspect the magnetron for any cracks or physical damage.
- Test the continuity and resistance of the magnetron using a multimeter.
- Test the High Voltage Transformer
- Verifying the resistance of the high-voltage transformer’s primary and secondary windings is essential.
- Test the isolation of the windings to the core.
- The primary winding should have a resistance of less than 1 ohm, and the secondary winding should have a resistance of 80-120 ohms to the core.
- Check the Fuse on the Filtering Board
- Locate the fuse on the filtering board.
- Ensure it is not blown by testing for continuity using a multimeter.
- Test the Micro Switches and Cherry Switches
- Check the operation of the microswitches and cherry switches responsible for detecting the door open/close status.
- Replace any faulty switches to ensure proper door detection.
- Test the PC-Mounted Transformer
- The PC-mounted transformer powers the display.
- Check the resistance of the windings and isolation to the core.
- The transformer should have a resistance of 400 ohms between the windings and no connection to the core.
- The 11V secondary winding should measure around 12 ohms, and the 5.5V winding should measure around 4 ohms.
If any of these components fail the tests or show signs of damage, replace them with new ones. Faulty electrical components can cause erratic behavior, such as the microwave turning on by itself or shutting off prematurely.
Troubleshooting Tips
Consult Repair Videos
Before attempting any repairs, consider consulting online video resources that provide guidance and visual demonstrations for troubleshooting and repairing Sharp microwave models. These videos can offer valuable insights and step-by-step instructions, saving time and effort.
Discharge the Capacitor Safely
Always discharge the high voltage capacitor before working on the microwave’s internal components as a crucial safety precaution. Failure to do so can result in a potentially dangerous electric shock. Follow the proper procedure to safely discharge the capacitor using a 20K ohm resistor tool.
Check Door Switch Symptoms
Malfunctioning door switches can cause various issues, including:
- The microwave prompts you to open and close the door, even when you have already done so.
- The fan and turntable operate while the door is open.
- The countdown timer runs, but the microwave doesn’t start heating.
- The turntable and heating functions don’t work, but other cook cycle features usually operate.
Understand Door Switch Types
Most microwaves have three door switches:
- Primary Interlock Door Switch: This switch is crucial for the microwave to function. The microwave won’t heat up if it’s faulty, even if other components work correctly.
- Door Sensing Switch: Connected directly to the control board, this switch turns off the light, fan, and turntable when the door is opened.
- Monitor Switch: A safety switch that blows a fuse if the other two-door switches fail to open when the door is opened.
Interpret Error Codes in the Microwave
It is essential to pay close attention to any error codes appearing on the panel for control, as they can indicate particular issues.
Error Code
Potential Issue
EE1, EE2
Magnetron failure
EE3
Both magnetrons failed
EE4
Voltage too high
EE5
Voltage too low
EE6, EE10, EE16
Thermistor failure
EE7
Exhaust air temperature too high
EE8
Circuit failure
EE9
Maximum time exceeded
EE0
Fan lock error
EE17
Magnetron temperature too high
Consider Cost-Effective Repairs
Repairing the microwave for minor issues like broken buttons or encoders can be more cost-effective than purchasing a new one. With some basic troubleshooting and repair skills, many microwave problems can be fixed at home, saving you money in the long run.
Maintain and Clean Regularly
With adequate cleaning and maintenance, your microwave can endure much longer. To guarantee maximum efficiency and avoid any potential problems, it is crucial to adhere to the cleaning and maintenance guidelines suggested by the manufacturer.
Conclusion
Resolving a Sharp microwave that only runs for a few seconds before shutting off can be challenging. Still, it’s possible to identify and address the underlying issue with the right troubleshooting approach.
Whether it’s a faulty door switch, a control panel glitch, or an electrical component failure, following the step-by-step instructions outlined in this guide can help you pinpoint and rectify the problem effectively.
By systematically inspecting the door switches, testing the control panel, and thoroughly examining the electrical components, you can eliminate potential causes one by one.
If you still encounter difficulties, consult online repair videos or seek professional assistance from trusted resources. With patience and perseverance, you can run your Sharp microwave smoothly again, ensuring convenient and efficient meal preparation for years.
F.A.Q.s
Q: What could be the reason why my microwave ceased operation after 3 seconds?
A: Your microwave may be experiencing issues that will cause it to shut off shortly after starting. This could be due to various reasons, including overheating, a malfunctioning component, or a safety feature being triggered.
Q: What might cause my microwave to turn off immediately upon starting?
A: If your microwave shuts down instantly, it might be overheating, which causes the high-voltage parts inside to get too hot. This activates the thermal cut-out switch, a safety mechanism to prevent further overheating.
Q: What are the potential reasons for my Thermador microwave to stop running after a few seconds?
A: If your Thermador microwave stops working briefly, it could indicate that the magnetron isn’t drawing the necessary power. This issue could stem from a faulty magnetron, a defective inverter board, or an improperly activated door switch.
Q: What could cause my microwave to stop working sporadically?
A: Multiple factors could lead to your microwave randomly ceasing to function. These include a malfunctioning diode, burned-out high-voltage capacitors, transformers, or an overheated Thermo protector.