Bosch Refrigerator Error E28 — Defrost Fix

What Does This Error Mean?

Bosch fridge E28 means the automatic defrost system has failed — the defrost heater or defrost thermostat is not working. As a first step, manually defrost the fridge by switching it off and leaving the door open for 24 hours — this clears the ice blockage and sometimes resets E28. If E28 returns after manual defrost, the defrost heater or thermostat has failed and needs replacing.

Affected Models

Bosch Series 2 Fridge-Freezer
Bosch Series 4 Fridge-Freezer
Bosch Series 6 Fridge-Freezer
Bosch KGN Series
Bosch KGF NoFrost Series

Common Causes

Defrost heater element failed — it no longer melts the frost on the evaporator coils during automatic defrost cycles
Defrost thermostat failed in the open position, preventing the defrost heater from receiving power
Defrost control relay on the main board has failed
Evaporator so heavily iced over that the defrost heater cannot reach the thermostat
Wiring to the defrost heater broken or a connector corroded

How to Fix It

Manually defrost the fridge-freezer

Remove all food, switch the fridge off, and leave all doors open for 24 hours. Place towels on the floor to catch meltwater. This clears any ice blockage that was preventing the defrost sensor from resetting.
Check if E28 clears after defrost

After manual defrost, wipe out all moisture, then switch the fridge back on. If E28 clears and the fridge cools normally, the manual defrost broke the cycle. Monitor over 48 hours — if ice returns quickly, the defrost heater has failed.
Access the evaporator panel

With the fridge off, remove the freezer shelves and the rear inner plastic panel (usually 4–6 screws). Behind it is the evaporator coil and the defrost heater running along the coil.
Test the defrost heater

Disconnect the defrost heater wiring connector. Use a multimeter set to resistance — a working heater reads 20–80 Ω. A reading of OL (open circuit) means the heater element has burnt out and needs replacing.
Replace the defrost heater

Order the heater assembly for your Bosch model — it clips around the evaporator coil with brackets. Disconnect the old heater, fit the new one, reconnect the wiring, and refit the evaporator panel. Cost is typically $30–60.

When to Call a Professional

Testing and replacing the defrost heater requires accessing the evaporator panel inside the freezer compartment. This involves removing the freezer shelves and the rear inner panel. If unsure, contact Bosch service.

Frequently Asked Questions

How do I know if my fridge's defrost heater has failed?

The signs are: ice forming on the back wall of the freezer that does not melt on its own, reduced cooling in the fridge section, and a cracking sound from the freezer. Combined with E28, these symptoms confirm defrost heater failure.

Will manually defrosting permanently fix Bosch E28?

Manual defrost clears the symptom but not the cause. The automatic defrost system will fail again — typically within 2–8 weeks — because the heater or thermostat has not been repaired. Manual defrost buys time while you order parts.

How often should a Bosch fridge auto-defrost?

Bosch fridge-freezers typically run a defrost cycle every 8–12 hours, usually overnight. Each defrost cycle lasts 20–30 minutes. If ice builds up consistently, the defrost cycle has stopped running.