Bosch E33
Excess Foam
Low severityExpert Guide
SeverityLow
What Your Machine Is Actually Telling You
E33 is Bosch's heater circuit error. The board applied power to the heating element but the temperature sensor (NTC) didn't register the expected temperature rise. The board waits a defined period and if water temp doesn't increase, it throws E33.
Bosch heating elements are typically U-shaped metal tubes mounted through the outer tub wall, submerged in wash water. They operate at 1800-2400W, drawing 8-10A. The element is controlled by a relay or triac on the main board.
How Bosch verifies heating: The NTC thermistor near the element monitors temperature. The board expects to see a 0.5-1°C rise per minute depending on water volume. If the sensor shows no rise after 5-8 minutes — E33.
Common causes:
1. Element burned out (45%) — the internal heating wire breaks. Resistance goes from ~20Ω to OL (infinity).
2. Element grounding (15%) — insulation breakdown allows current to leak to the tub casing. Trips GFCI/RCD breakers.
3. Wiring failure (15%) — corroded connectors or broken wire between board and element.
4. NTC sensor failure (15%) — the temperature sensor is bad so the board can't detect heating (even though the element itself works).
5. Board relay failure (10%) — the relay controlling the element is stuck open.
Limescale connection: Hard water deposits limescale on the element surface. The scale insulates the element, reducing heat transfer to water. This makes the element run hotter internally, accelerating its demise. Regular descaling extends element life significantly.
Bosch heating elements are typically U-shaped metal tubes mounted through the outer tub wall, submerged in wash water. They operate at 1800-2400W, drawing 8-10A. The element is controlled by a relay or triac on the main board.
How Bosch verifies heating: The NTC thermistor near the element monitors temperature. The board expects to see a 0.5-1°C rise per minute depending on water volume. If the sensor shows no rise after 5-8 minutes — E33.
Common causes:
1. Element burned out (45%) — the internal heating wire breaks. Resistance goes from ~20Ω to OL (infinity).
2. Element grounding (15%) — insulation breakdown allows current to leak to the tub casing. Trips GFCI/RCD breakers.
3. Wiring failure (15%) — corroded connectors or broken wire between board and element.
4. NTC sensor failure (15%) — the temperature sensor is bad so the board can't detect heating (even though the element itself works).
5. Board relay failure (10%) — the relay controlling the element is stuck open.
Limescale connection: Hard water deposits limescale on the element surface. The scale insulates the element, reducing heat transfer to water. This makes the element run hotter internally, accelerating its demise. Regular descaling extends element life significantly.
What You're Probably Seeing Right Now
- Hot/warm wash cycles produce cold water — feel the door glass 15 min into a 60°C cycle.
- Your GFCI/RCD breaker trips when the machine runs — element is grounding to the tub.
- Cold cycles work fine — they don't use the heater.
- Clothes come out less clean than before — hot water is essential for removing oils and bacteria.
- E33 appears partway through the cycle — when the heating phase should begin.
DIY Fix — From Easiest to Hardest
1
Confirm No Heating (3 minutes)
1. Start a **60°C Cotton** cycle.
2. Wait 15 minutes.
3. Feel the door glass.
4. **Warm/hot glass** = element works, NTC may be the issue.
5. **Cold glass** = element is dead or not receiving power.
2. Wait 15 minutes.
3. Feel the door glass.
4. **Warm/hot glass** = element works, NTC may be the issue.
5. **Cold glass** = element is dead or not receiving power.
2
Check the GFCI/RCD Breaker (1 minute)
If your breaker trips during wash:
1. This strongly suggests an **element grounding fault.**
2. The element insulation has broken down, leaking current to the tub.
3. **Do not bypass the breaker** — this is a safety device protecting you from electric shock.
1. This strongly suggests an **element grounding fault.**
2. The element insulation has broken down, leaking current to the tub.
3. **Do not bypass the breaker** — this is a safety device protecting you from electric shock.
3
Test the Heating Element (5 minutes)
1. Unplug machine. Remove back panel.
2. Locate element terminals — 2 pins at the bottom of the tub.
3. Disconnect wires.
4. **Resistance test:** 20-30Ω = good. OL = dead (replace).
5. **Ground fault test:** Probe between element terminal and tub casing. Should be OL. Any reading = grounding fault (replace).
**Test both terminals to ground** — either can fail independently.
2. Locate element terminals — 2 pins at the bottom of the tub.
3. Disconnect wires.
4. **Resistance test:** 20-30Ω = good. OL = dead (replace).
5. **Ground fault test:** Probe between element terminal and tub casing. Should be OL. Any reading = grounding fault (replace).
**Test both terminals to ground** — either can fail independently.
4
Replace the Heating Element (20 minutes)
1. Remove the single center nut/bolt holding the element.
2. Press the stud inward to release the internal rubber gasket.
3. Carefully wiggle the element out — work past any scale deposits.
4. Clean the mounting hole of old gasket material and limescale.
5. Slide in new element — ensure gasket seats evenly.
6. Tighten nut gradually — don't overtighten (can distort gasket).
7. Reconnect wires and NTC.
**While the element is out:** Pour a cup of descaler into the hole to clean the inner tub.
**Order using E-Nr** — Bosch elements are model-specific.
2. Press the stud inward to release the internal rubber gasket.
3. Carefully wiggle the element out — work past any scale deposits.
4. Clean the mounting hole of old gasket material and limescale.
5. Slide in new element — ensure gasket seats evenly.
6. Tighten nut gradually — don't overtighten (can distort gasket).
7. Reconnect wires and NTC.
**While the element is out:** Pour a cup of descaler into the hole to clean the inner tub.
**Order using E-Nr** — Bosch elements are model-specific.
5
Check the NTC Sensor (5 minutes)
The NTC is usually mounted in or near the element:
1. Disconnect NTC wires.
2. Measure resistance: **~10,000Ω at 20°C — should decrease when warmed.**
3. OL or 0Ω = dead NTC — replace.
4. NTC costs $10-25 and takes 2 minutes to swap.
1. Disconnect NTC wires.
2. Measure resistance: **~10,000Ω at 20°C — should decrease when warmed.**
3. OL or 0Ω = dead NTC — replace.
4. NTC costs $10-25 and takes 2 minutes to swap.
6
Descale to Prevent Future Failures
After replacing the element:
1. Run a **90°C empty cycle** with descaler or 2 cups of white vinegar.
2. Repeat monthly in hard water areas.
3. Consider installing an **inline water softener** or whole-house softener.
**Bosch's Drum Clean** program at 90°C helps dissolve scale buildup.
1. Run a **90°C empty cycle** with descaler or 2 cups of white vinegar.
2. Repeat monthly in hard water areas.
3. Consider installing an **inline water softener** or whole-house softener.
**Bosch's Drum Clean** program at 90°C helps dissolve scale buildup.
When to Call a Pro
- •Element grounding — breaker tripping — urgent. Element replacement: $120-$250 installed.
- •Element AND NTC both failed — combined replacement: $150-$300.
- •Board relay failure — board repair: $150-$400.
- •Severe limescale damage — element seized in tub wall. Requires careful extraction: $150-$300.
What It'll Cost You
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