Bosch Cooktop Error Code ER 26

ER 26 means the cooktop has detected that the relay supply voltage is too high while the control is in the off state. Normally, the relay circuit should show little to no voltage when not energized. This fault is flagged by the control electronics to prevent unsafe operation and potential component damage. It points to an issue with the control board, relay assembly, or associated wiring.

You should not continue using the cooktop while ER 26 is active. This fault indicates abnormal voltage in the relay circuit during the off state, which could mean a relay is not switching off correctly. Continuing to operate the unit risks a heating element remaining energized unintentionally, which is a safety hazard. Disconnect power until the fault is diagnosed and repaired.

Repair costs vary depending on the root cause. A wiring harness repair may cost between $75 and $150 in labor if no parts are needed. Control board replacement on a Bosch cooktop typically runs between $200 and $450 including parts and labor, depending on the model. Relay replacement alone is generally less expensive, often in the $100 to $250 range with a service call included.

Diagnosing ER 26 requires safely accessing the control board and relay components, which involves working near line-voltage wiring. A knowledgeable DIYer comfortable with appliance electronics can inspect wiring harnesses for visible damage, but testing relay coil resistance and identifying board-level component failures typically requires a multimeter and experience with control board diagnostics. If the control board or relay needs replacement, a qualified technician is recommended.

Resetting the cooktop by cutting power at the breaker and restoring it may temporarily clear the display, but ER 26 will return if the underlying fault in the relay circuit or control board is still present. A reset does not repair a welded relay, a leaking switching component, or a wiring fault. Persistent recurrence of ER 26 after a reset confirms that a component repair or replacement is needed.