When your Bosch dryer throws an E28, it’s telling you the electronics detected a fault. In most cases that lives somewhere between the control board, its wiring harness, and the sensor circuits that report temperature and moisture. Sometimes it’s a one-off software hiccup after a surge or brownout; other times it’s a genuine hardware issue like a failing relay/triac on the board, a corroded connector, or a sensor line shorted to ground.

Start simple

Power the dryer off, unplug it, wait ten to fifteen minutes, then plug it back in and try again. That pause lets the capacitors discharge and gives the control a clean restart. If the machine is on an extension cord, power strip, or shared high-load circuit, move it to a dedicated outlet—the control is sensitive to voltage dips, and dirty power can trigger E28 even when nothing is actually broken. After the reboot, close the door firmly and start a short timed-dry cycle. If E28 disappears and the dryer runs normally, you likely hit a transient glitch. If it reappears immediately, you’re past the “quick fix” stage.

From there, a careful visual once-over can save time. With the dryer unplugged, remove the lint filter and look down into the housing where the two stainless moisture-sensor bars sit; if they’re coated in fabric softener residue, clean them with isopropyl alcohol on a soft cloth. Residue can confuse the sensing circuit and occasionally contributes to control faults. Next, check the power cord and terminal block at the rear of the dryer for heat discoloration or loosened screws. Any signs of burning or melted plastic are a stop-now and call-a-pro situation. If you’re comfortable opening panels, inspect the main wiring harness for pinched or rubbed insulation, especially where it passes around sharp brackets; Bosch looms are neat, but a shifted clip or vibration can still chafe a wire.

If E28 persists, the usual suspects are the main PCB (control board), the user-interface board/cable, or a sensor circuit (NTC temperature probe or moisture-sensor wiring). A technician will drop the machine into service mode, pull any stored sub-codes, and then isolate the fault by checking continuity and resistance on the relevant connectors. On heat-pump models, they’ll also confirm the inverter and compressor control aren’t feeding noise back into the logic board. If a control is replaced, it’s common to see a quick firmware/configuration step so cycle options match your exact model; skipping that can lead to odd behavior even if the dryer “runs.”

It’s worth noting that E28 is an electronics category code, not a single part name. On some series, Bosch maps E28 to a specific sub-circuit in the tech sheet tucked behind the kick panel or rear cover. If you’re technically inclined, you can reference that sheet to measure the NTC probe (it typically reads in the tens of kilo-ohms at room temp) and verify harness integrity with a multimeter. But if your dryer is under warranty—or you’re not fully confident—don’t open the cabinet. Bosch controls are compact and expensive; a wrong move can turn a small repair into a big one.

A quick word on prevention

Good airflow doesn’t “fix” E28, but it keeps temperatures stable and reduces stress on the electronics. Clean the lint filter every load, keep the vent run short and clear, and avoid overloading. For condensation or heat-pump models, leave the door ajar for a few minutes after use to let moisture dissipate from the drum and control cavity. Stable power matters too: if you live in an area with frequent dips, a proper, electrician-installed surge suppressor can protect sensitive boards far better than a bargain power strip.

When should you call a Bosch dryer repair specialist?

If E28 returns after a proper power reset, if you see any burned connectors, if the drum won’t even attempt to start, or if the dryer now shows multiple codes, you’re at the point where professional diagnostics pay for themselves. A qualified tech will verify input power, run the machine’s self-tests, check sensor values under heat, and determine whether you’re looking at a harness repair, a board replacement, or a simpler cleaning/connection fix. They’ll also clear stored faults and run a final test cycle so the control can relearn normal values.

E28 means the control isn’t happy with what it’s seeing electrically. Try a true power reset on a clean, dedicated outlet and give the moisture sensors a proper cleaning. If the error comes back, skip the guesswork—electronics faults are where a Bosch-savvy technician shines, saving you time, money, and a second round of parts.