AEG Dryer Error EHO (EH0): Power Supply or Control Board Fault Diagnosis

User question

aeg error eho

Artificial Intelligence Response

Direct answer to the question

• EH0/EHO on AEG appliances means the control detects an abnormal mains power condition (voltage, frequency, interruption, or internal low‑voltage rail instability). On many AEG/Electrolux dryers it often traces to the power‑supply section of the main control board, but you must first rule out the wall supply and wiring.
• Related subcodes where available: EH1 = frequency out of range, EH2 = voltage too high, EH3 = voltage too low.

Key points

• Treat “EHO” as “EH0” (font/zero). It is a power‑supply error, not a heating/heat‑pump fault.
• Do basic external checks first (no extension leads, prove the wall outlet under load, try another circuit).
• If mains is good and the error recurs—especially mid‑cycle on dryers—the PCB’s switch‑mode power supply (SMPS) and its fusible resistor/capacitors are prime suspects.

Detailed problem analysis

1) What the controller is watching

• Zero‑cross/frequency monitor: The MCU expects steady 50/60 Hz zero‑cross pulses. Missing, noisy, or out‑of‑range pulses set EH1/EH0.
• DC rails from SMPS: The low‑voltage rails (e.g., 5 V/12 V) must be within tolerance with low ripple. Undervoltage/boot‑looping triggers EH0.
• AC line quality: Deep dips, high peaks, or interruptions (loose plug, weak outlet, overloaded circuit) can raise EH0.

2) Why dryers show EH0 mid‑cycle

• Transient load steps (compressor start, heater relays, fan motors) stress a borderline SMPS. A tired LNK/TNY‑family primary switch IC, open/changed fusible input resistor (~47 Ω), or high‑ESR electrolytics raises ripple; the MCU sees unstable Vcc or irregular zero‑cross and posts EH0.
• Hairline cracks on relay/transformer pins and carbonized fluff on the PCB add intermittent faults/leakage.

3) Typical root causes by location

• External
  • Extension cord/multiplug voltage drop.
  • Loose/oxidized receptacle, weak breaker, overloaded branch circuit.
  • Frequency anomalies (inverters/generators/UPS; rare on utility mains).
• Internal
  • SMPS primary switch IC (e.g., LNK36x/TNY series) degraded or shorted.
  • Open or drifted fusible input resistor (commonly 33–100 Ω; often 47 Ω).
  • Dried‑out 105 °C electrolytics (primary bulk cap, secondary filters).
  • Cracked solder joints on relays, power resistors, or the mains filter (EMI) board.
  • Failed EMI filter or NTC inrush limiter disturbing zero‑cross sensing.

4) Do not confuse with heating faults

• Heat‑pump/NTC problems do not generate EH0; they log different codes. If you see “EHO” it is almost always the power path or control board power section.

Current information and trends

• AEG/Electrolux service information groups EH0/EH1/EH2/EH3 as supply‑quality faults. Field repair forums and service videos consistently show recurring control‑board PSU failures on heat‑pump dryers leading to EH0, especially after several years of use.
• Trend: Many repairers now pre‑emptively replace the SMPS switch IC, fusible resistor, and electrolytics as a set to restore stability and extend board life.

Supporting explanations and details

• How a weak SMPS creates EH0: At motor/compressor start the rectified bus sags; with aged caps the controller IC hits UVLO, reboots (“ticking”), the MCU detects brownout/zero‑cross loss and stores EH0.
• Frequency subcode (EH1): If the zero‑cross detection circuit (opto/RC network) is noisy or the EMI filter is failing, the MCU may “see” frequency out of range even on good mains.

Ethical and legal aspects

• Mains‑side electronics are hazardous. Only qualified persons should service live‑side SMPS and EMI filters. Always unplug; discharge capacitors; use an isolation transformer for powered diagnostics.
• Replace fusible resistors with proper flameproof fusible types of the same value/wattage; never substitute generic wire‑wound parts.
• Maintain protective earth continuity; do not bypass safety components (NTC, MOVs, thermal fuses).
• Follow regional electrical codes (NEC/UL in the United States; ensure the appliance is suitable for 120/240 V, 60 Hz if installed in the US).

Practical guidelines

User‑level checks (5–10 minutes)

• Unplug extensions/multiplugs. Plug directly into a known‑good wall outlet.
• Prove the outlet: run a high‑load device (e.g., 1.5–2 kW space heater/kettle) on the same outlet; watch for dimming/flicker or warmth at the plug/outlet.
• Try another dedicated circuit (different room/breaker).
• Power‑cycle reset: unplug 5 minutes; re‑test.
• If your model supports it, enter service mode to read last alarm subcode (EH1/EH2/EH3). Procedure varies by PNC; commonly: machine OFF → hold Start/Pause + adjacent button → rotate selector one click clockwise; wait for LEDs to flash, then step to fault readout position.

Electrician checks (if any doubt about supply)

• Measure line voltage under load; should remain within nominal limits for your region (e.g., 230 V ±10% in EU installations; 240 V split‑phase in US laundry circuits).
• Verify tight, clean terminations at the receptacle and breaker; check for shared high loads on the same circuit.

Technician/engineer checks (appliance opened, unplugged)

• Visual on main PCB: darkened areas, cracked solder on relays/transformer, domed/leaking electrolytics, charred fusible resistor.
• Bench tests
  • Check the fusible input resistor (~47 Ω typical). If open/high, suspect the SMPS IC shorted.
  • Replace SMPS switcher IC (common families: LNK364/LNK304/TNY264, depending on board), the fusible resistor, and all PSU electrolytics with low‑ESR 105 °C parts.
  • Verify secondary rails (e.g., 5 V) ripple <50–100 mV with an oscilloscope.
  • Reflow suspect joints; clean lint/carbon deposits with proper solvent and allow to dry fully.
• If component repair is not desired, replace the configured main PCB matching the PNC; some boards need programming to the appliance.

Possible disclaimers or additional notes

• Model differences exist; button sequences for diagnostics and exact PSU parts vary by PNC. Always consult the service manual for your exact model.
• Intermittent EH0 can be environmental (weak circuit, shared loads) and may only appear during high‑draw phases; capture conditions when it occurs.

Suggestions for further research

• Obtain the service manual for your exact AEG model/PNC to confirm diagnostic mode and parts list.
• If frequent EH1 occurs while running from a generator/UPS/inverter, review its output waveform and THD; consider a true‑sine unit with adequate surge capacity.
• Investigate known board revisions for your model; some later PCBs improve PSU robustness.

Brief summary

• EH0/EHO on AEG indicates a mains/power‑supply fault. Eliminate external causes first (no extensions, verify outlet and circuit). If mains checks pass yet the error recurs, especially mid‑cycle on dryers, the main control board’s SMPS is likely failing—typically the primary switch IC, fusible resistor, and electrolytics. Repair at component level or replace the board.
• Provide your exact model/PNC and when the error appears (immediately, at start, or mid‑cycle), and I’ll outline a model‑specific diagnostic and parts list.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.