Common Sensor Faults in Touchscreen StovetopsStovetops with touch control look stylish, are easy to use, and power efficient. That is why they keep winning more and more customers. However, even these advanced kitchen appliances may have some troubles. Sometimes sensors are not reacting to your touches or a burner is just not turning on. There can be many causes to handle.Sensor designA sensor usually stops functioning when the operation rules are not followed. As a rule, a fault can be fixed by following the manufacturer’s recommendations without calling a repairman. You should know what problems can be solved by yourself, and what problems require calling a service center. And above all, you should understand the operation principle of stovetop sensors. A sensor looks like a spring with a metal base fastened on a printed circuit board (PCB):Metal springs are also used as current conductors. Plastic spring models employ additional conductors to connect a metal base with a PCB.The stovetop sensor operation principle is illustrated in the following diagram:The human body is a kind of capacitor with certain electric capacity. For example, it can be clearly seen when you touch a radio antenna with your hand. This improves or impairs the radio reception quality.When you touch a sensor, the body capacity increases the touch area capacity. A microcontroller perceives the change and switches on the corresponding stovetop mode.This sensor type is called a capacitive sensor. Since the human body capacity is transmitted indirectly through a ceramic glass, this specific sensor type is called a projected capacitive sensor. Touchscreen stovetop control diagramThe functional control of a touchscreen stovetop consists of the three blocks:

• TOUCHSCREEN
• CONTROL UNIT
• POWER UNIT.

Low-current microcontroller cannot control the burners directly. They are switched on with a 12V electromagnetic relay. A 5V microcontroller needs an intermediary to start this relay. This intermediary is a power driver. The most common driver is microcircuit ULN2003a — it is a Darlington transistor circuit with high-power output switches.A microcontroller is connected to the burner sensors, and after receiving a touchscreen signal, it switches on the burners for a specific time required to reach the temperature selected by a user. Initial troubleshooting If a stovetop is not turning on or not working, you should first check the voltage availability. Stovetops are high-power units that are usually connected to a separate power line. You will probably not be able to check the line voltage by connecting other serviceable electric devices. A stovetop is connected to a separate outlet with a special plug designed for the 40 Amp current. That is why you should check the voltage in the stovetop connection outlet. The voltage can be checked either with a test screwdriver or a multimeter. The former will indicate the voltage availability with a test screwdriver diode light. The latter can additionally determine the voltage. This is very important since the stovetop electronics prevent operation with too low or high voltage.If voltage is unavailable in the outlet, check the circuit breaker of the separate line for voltage availability and triggering. If voltage is available in the socket, disconnect the stovetop power cable and check it for continuity and breakdowns, as well as for plug contact oxidation.“Important! Check the cable and inspect the fuse only after powering off the appliance.”If a circuit breaker or stovetop input fuse keeps triggering, it means the stovetop has a serious fault. In this situation, manufacturers insist on calling a qualified technician.Users with sufficient skills and expertise in handling electric appliances can continue self-troubleshooting. However, this may require you to remove and partially disassemble the stovetop. Stovetop removal and partial disassembling Make sure the stovetop is powered off before proceeding with the removal. After that, detach the adhesive table sealing and push the stovetop up from the bottom to take it out from the installation spot. Take off the ceramic glass to complete the partial stovetop disassembling. It is fastened either with screws or with special mounting clips that must be pressed down with a screwdriver.When the ceramic glass is removed, all stovetop units will be available for inspection and check. Stovetop error codes In case of a failure, modern stovetops display error codes on the control panel to determine and promptly correct the encountered problem. The stovetop error codes of some manufacturers are listed in the table below: 

Errors	Stovetop codes
	Gorenje	Samsung	Zanussi	Hansa	Whirlpool	Bosch
Sensor is active for over 10 seconds	F0	SE
More than two buttons pressed simultaneously		SE3
Wet cloth on touch buttons		SE1
Liquid, water, leftover food on the touch panel	ER22	SE2				E
Control board fault						F5
Surface overheating	F2	Ot		E/4	E2	F2
Burner overheating (coil inductions, fan failure)			E4	E/8
Electronics overheating			E1		C81, C82
Power line error (open, short circuit, parameter mismatch)	U400, F1		E5		С83, C84, F02, F04
Induction module power off				E5
Unit failure	F2 , F3, F4, F6		E3, E6, E8	Е / А, E/9		FO
Configuration error			E9	Е / С
Unexplained failure				E/2
Incompatible cookware	F5				C85

 You can find more details about every problem that can be self-solved in the documentation of your stovetop. We recommend making a table with stovetop codes and keeping it at hand in your kitchen. Most sensor faults can be solved on your own by restarting the stovetop. To do that, unplug the stovetop for a few minutes. If it doesn’t help to bring the stovetop back to normal, call a service center.Sensor failure causesLoose plastic springs Does ceramic glass impair the contact between a finger and sensor? Certainly not. The glass permittivity ε is 4-16 units. This is enough even for a 18 mm thick glass. However, a sensor will stop working right when the contact between the spring top surface and ceramic glass is loose. This may happen if plastic springs have been affected by heat for a long time. Even a tiny gap will create an air obstacle for electric capacity with very low permittivity of ε=1,00054.

Environment permittivity
Medium	ε
Vacuum	1
Air (dry)	1.00054
Dry paper	2-2.5
Line seed oil	3.2-3.5
Olive oil	3.1
Cotton oil	3.1
Glass	4-16
Salt	5-6
Water	80.4

Problem solution: partially disassemble the stovetop and replace the spring. You can also install additional plastic washers. This problem is not typical of metal springs.Sensor fault Plastic springs may have other potential problems apart from being loose. Long-term heat impact may lead to their destruction. Such rare faults may result in the sensor metal base touching the board current-carrying tracks. Problem solution: partially disassemble the stovetop, replace the springs or, if necessary, the board.Water on control panel This is actually not a sensor fault. However, the stovetop will not be working. Manufacturers made provision for this kind of improper operation — In case of a relevant failure, the corresponding error code will appear on the control panel. Why water on the control panel results in sensor failure? Let’s find it out with the following example:When you touch a mid-circuit sensor with your finger, your body shares electric capacity with other neighboring sensors as well. When the surface is dry, the left-circuit sensor receives much less electric capacity from you as its contact surface is far from the touch point. But water with high permittivity ε = 80 allows the right-circuit sensor to receive human electric capacity equal to that of the mid-circuit sensor. The microcontroller receives it as pressing two sensors (or more if there’s much water) simultaneously and refuses to run the command. Problem solution: Clean the stovetop surface and restart it.Activated interlock A common reason for a stovetop not turning on is a safety interlock. You just need to unlock it to solve the problem. The unlocking procedure slightly differs for different stovetop models.Foreign objects on control panel  The situation is similar to spilled water on the control panel. Any foreign object on the control panel affects the electric capacity of sensors. The microcontroller receives it as a long (more than 10 seconds) sensor pressing and activates stovetop interlocking. Problem solution: Remove a foreign object from the control panel, and restart the stovetop.Moisture ingress in stovetop body This is quite a rare problem that may appear in case of improper stovetop installation. Most manufacturers prohibit installation of this appliance in the worktop without special sealing. A sealant applied along the stovetop edges prevents ingression of water inside the worktop.When a stovetop is installed flush with the worktop, the gap between the stovetop and worktop must be filled all along the edges with a silicone sealant able to withstand at least 320 °F.This will prevent ingression of water from the surface to under the panel and inside the stovetop body. It may damage not only the sensor panel but also other stovetop units. Problem solution: Remove the panel, replace faulty units, and install the panel again following all manufacturer’s instructions.Capacitor fault Long-term stovetop operation may result in problems with electrolytic capacitors of the power unit. This is facilitated by high temperatures inside the stovetop body. Usually, a faulty capacitor can be detected visually. The body of a faulty capacitor is swollen, while electrolytes can eat through the board contacts and traces. Problem solution: Replace capacitors, restore damaged traces and contacts, and replace the unit completely.Burnt contacts of burner relay If only one burner is not working, it clearly indicates a faulty relay. Problem solution: Replace the relayFaulty control unit This is the most unpleasant situation. This fault can be identified with an error code appearing on the control panel. For example, Bosch stovetops will show an F5 error code (Faulty control panel). Problem solution: reflash the control unit processor or replace the unit completely. In this case, the decision is up to the specialist.Preventive maintenance The surface of such a stovetop is quite delicate. Any water or dirt can significantly impair the operation. That is why you should remove any dirt in good time without damaging the stovetop. Use a special scraper to remove dried grime.Before using a scraper, soak the grime in a special cleaning agent.For that, use a soft sponge.Remove dissolved grime with a soft textile tissue.Do not use the following items to clean the stovetop surface:

• spot remover
• sprays for ovens
• old hard and coarse sponges and cloth
• knives, mesh brushes, and sponges with metal and abrasive parts
• hard paper
• Cleaning agents with abrasive materials

The most important part of preventive maintenance is careful reading and following instructions of the stovetop manufacturer.