Thermador Dishwasher Not Heating

Use only checks that match the exact appliance or system and its official guide.

1. Check 1

   After a completed cycle, compare glass or metal items with plastic items and feel the dishware only after the cycle has ended and it is safe to do so. Note whether the tub and nonplastic items are warm, whether dishes are merely wet, or whether everything is cold and the wash result is poor.

   Expected result: Only plastics are wet, the final-rinse dishware is warm, or the entire load and tub are cold with poor cleaning.

   Next step: Continue with cycle, rinse-aid, water, and filter checks for a cold-load symptom. Do not order a heater from wet plastics alone; request service if the complete load remains cold.

   Why this matters

   Why: Thermador describes condensation drying and says plastics do not heat as much as glass or porcelain. A cold load with poor cleaning is less consistent with normal condensation drying and keeps incoming water, cycle selection, limescale, or a heating fault in consideration.

2. Check 2

   Check the selected program and options in the exact Thermador manual. Confirm that a cycle with drying was selected and, where the model provides it, check whether Extra Dry is available and enabled. Do not assume every cycle or model has the same option.

   Expected result: A no-dry cycle was selected, Extra Dry is available but off, or the cycle includes drying and the load is still cold or wet.

   Next step: Run one normal cycle with the model-approved drying option. If the same cycle remains cold or a fault returns, stop owner testing and use Thermador service.

   Why this matters

   Why: Thermador lists a cycle without drying as a common reason for poor drying and says Extra Dry is available only on select models. Correcting the option can explain wet dishes; it does not explain a fully cold wash or a heater fault code.

3. Check 3

   Check the rinse-aid level and refill it only with the product and procedure specified by the exact model manual. Arrange dishes so they slope and do not nest, then compare the next completed cycle with the previous result.

   Expected result: Rinse aid was empty, dishware was flat or nested, or rinse aid and loading were already appropriate but drying remains poor.

   Next step: Correct the documented rinse-aid or loading condition and monitor one cycle. If nonplastic items and the tub remain cold, continue to the water and service checks rather than increasing detergent or disassembling the appliance.

   Why this matters

   Why: Thermador says rinse aid improves condensation drying and that loading angle and spacing affect runoff. These conditions can leave water without proving that the dishwasher is failing to heat.

4. Check 4

   Before starting a cycle, run the hot-water faucet nearest the dishwasher briefly as Thermador recommends for a long-cycle symptom, then confirm the dishwasher is connected to the intended hot-water supply and that the inlet line is not visibly kinked. Do not disconnect plumbing while pressurized.

   Expected result: Incoming water was cold, the cycle is unusually long, the supply line is kinked, or the water supply and cycle length appear normal.

   Next step: Correct only a visible accessible kink or use the installation manual for supply questions. If water remains cold, the cycle never reaches its normal result, or a heater code appears, arrange qualified Thermador service.

   Why this matters

   Why: Thermador says incoming water that is not hot enough can extend a cycle while the internal heat pump heats it, and a cold-water connection can also lengthen the cycle. A normal supply does not rule out a heating-system fault.

5. Check 5

   Inspect the filter, spray-arm openings, and visible tub for food debris or limescale. Rinse the user-removable filter and clear only accessible debris according to the exact manual; if limescale is present, use only the model-approved descaling procedure. Do not reach into a heater, pump, or wiring area.

   Expected result: The filter or spray arms are blocked, limescale is visible, the tub is clear, or cleaning does not change the cold or poor-wash symptom.

   Next step: Reinstall the filter and run one model-approved cycle after a safe cleaning. If limescale is heavy, a heat-pump/heater code appears, or the symptom persists, stop and contact Thermador support.

   Why this matters

   Why: Thermador links blocked filters and spray arms to poor wash results and says limescale can build up in the heat pump and damage the heating system. Cleaning may improve circulation or a documented descaling path, but it does not prove the heater works.

6. Check 6

   Record any exact code, flashing pattern, water in the base, leakage, smoke, burning odor, or electrical smell from the display and manual. Do not reset repeatedly or open the appliance to test a heater; if a code is not listed, treat it as a service condition.

   Expected result: A heater or heat-pump fault is displayed, a safety or leak code is displayed, no code is present, or the code returns after the model-approved reset.

   Next step: Follow only the exact code instruction; stop the dishwasher and turn off water for a leakage-protection indication. Arrange Thermador service for a recurring, heater-related, unlisted, or safety code.

   Why this matters

   Why: Thermador's error-code guidance identifies heater electronics, heat-pump heater, limescale, leakage protection, and other faults with model-specific next steps. A recurring or unlisted code cannot be narrowed safely from a symptom-only article.