I have a electric cooktop,when I turn on a burner the one next to it turns on as well .If I take the other cartridge and swap it out, it does the exact same thing.It is brand new unit right out of the box.It is 25 years old,and it has never been used.

Sounds like you may have a bad harness or bad infinite switch, you can test it with a multi meter.

Surface burners
are typically either a coil type, solid type or a ribbon coil as used in smooth top ranges. All of these consist of a heating wire that uses electric current to produce heat. Coil type elements can be checked for continuity by removing them from the terminal block and testing them with a multi-meter.You should also inspect the terminal ends for signs of heat damage or corrosion, and if present, you should replace the terminal block or receptacle at the same time. You will need to remove power from the range to change the terminal block. Solid elements and smooth top elements require raising or removing the main top to gain access. You will need to remove power from the range before lifting the main top. Continuity can then be checked with a multi-meter, once you have removed the wires from the element terminals.

On modern electronic control ranges,the oven temperature sensor
is the part thatregulates the oven temperature. If it is not working properly it could be the reason why the range or oven won't start. This part can be found inside the oven on the rear wall near the top. Most modern ovens will display a fault code if the oven sensor is at fault. If you think the sensor may be the issue you can check the resistance with a multi-meterbut will need to know the correctresistance of the sensor at room temperature. Remove power from the appliance before performing this test.

The infinite switch
on the control panel controls the power to each surface element. If you have no heat at an element and the element and terminal block check ok, then you may have a defective infinite switch. Disconnect power to the range and remove the console back panel. Locate the switch and check foroverheated wires or faulty terminals first.Test the switch's contacts for continuity with a multi-meter. If defective, replace the switch.

1. If the infinite switch does not appear to be defective, then you should check for proper voltage to the switch. This is a live high voltage test and should only be performed by qualified persons.(Locate the suspect switch for testing. Label all wires and terminals before disconnecting. A close up digital photo may be helpful.

1. On the burner control switch the terminal labeled "P" leads to the burner indicator light. The terminals labeled "H1" and "H2" lead to the burner element and the terminals labeled "L1" and "L2" (sometimes "N1" and "N2") are the power supply wires.

1. Set yourmultimeterto ohms setting x1. Turn the burner control to the highest temperature setting. Place one probe on pin "L1" and the second probe on pin "H1". The resistance measurement should be very low, zero to twenty ohms. If the test shows high or infinite resistance, the burner switch is defective.

1. Repeat the step above for the terminals "L2" and "H2".

1. If the control passes that test, turn the temperature setting to about the middle of the range and repeat the previous two steps. This will test for an intermittent problem with the switch. If the test does not show continuity with very low resistance, the switch should be replaced.

1. With the switch turned to the "Off" position, the resistance on each of the pairs of terminals tested above should now show no continuity or a reading of infinite resistance.

1. A test for continuity between "P" and "L1" when the burner control switch is on should show continuity. The light should be on whenever the control is turned on. If your test shows continuity, but the light does not operate, it is likely the bulb has failed.

If the burner switch shows high or infinite resistance, the switch is not passing along current to the burner and so the switch should be replaced. )

Most modern ovens usean electronic control board
to control the oven functions. These models will use the control board to operate the oven safety valve on a gas range or oven, and the bake and broil elements on an electric range or oven. If there is no power to the igniter circuit, or the element circuits, then you should check the control board to verify that there is power at the appropriate output relay. These are live voltage checks and should be performed by qualified persons only. If there is no output voltage then the control should be replaced.

The oven burner igniter
commonly known as the hot surface igniter is used in modern gas oven burners to open the gas valve and to ignite the gas. As the igniter draws electric current it will heat to a high temperature and glow, as well as cause the bi-metal in the oven safety valve to warp and open the valve releasing the gas to be ignited. This sequence normally takes about a minute. Igniters come in both flat and round styles and are very fragile. If the burner does not light then you should check the igniter first. If the igniter does not glow at all, then check for power to the circuit. This is a live voltage check and should be performed by a qualified person. If power is present then the igniter may be open circuit and can be checked for continuity with a multi-meter.If the igniter is glowing, but the burner is not lighting, the igniter may be weak and still be at fault because it requires a certain amount of current draw to open the valve.This check requires the use of an amp meter and should be performed by a qualified person. If the igniter is defective then it must be replaced.


http://www.partselect.com/Repair/Range-Stove-Oven/Will-Not-Start/



https://www.repairclinic.com/RepairHelp/How-To-Fix-A-Range-Stove-Oven/18---/Oven-won-t-turn-on-




if the harness is damaged it may effect any of the others down the line as well causing the burners to act up as they are wired in series