Bosch dishwashers are among the better machines we work on, and a large share of the calls we take about them are not faults at all. Two error codes and one design characteristic account for most of it.
The damp-plastics complaint, which is the machine working correctly
This is the single most common Bosch call, and there is nothing to repair.
Most manufacturers dry with a heating element in the base — hot air, wet dishes, water evaporates. Bosch's condensation drying has no element. It uses a stainless tub, which cools faster than the load, so moisture leaves the dishes and condenses on the tub wall and runs down the drain. It is quieter, it uses less power, and it will not warp a plastic container.
It also does not dry plastic. Glass and ceramic hold heat and shed their moisture; plastic has almost no thermal mass, cools instantly, and stays wet. That is inherent to the method.
What genuinely helps:
- •Use rinse aid, and keep it topped up. On a condensation-drying machine this is not optional. It changes the surface tension so water sheets off instead of beading, and the difference is dramatic. If your Bosch has got worse at drying, an empty rinse-aid reservoir is the first thing to check.
- •Load plastics on the top rack, and lying at an angle rather than flat, so water cannot pool.
- •Crack the door at the end of the cycle and let the residual heat out. Ten minutes does most of the work.
- •Use the extra-dry or Sanitize option if the model has one.
If somebody has quoted you a repair for wet plastics on a Bosch, get a second opinion.
E24 and E25: it is not draining
E24 is a drain fault — the machine did not empty in the time allowed. E25 is the closely related pump-blocked code. Together they are the most common genuine Bosch fault, and they are usually not a part.
Work through it in this order:
The filter assembly. Bottom of the tub, twist out the cylindrical filter and lift out the flat mesh below it. Bosch machines have no food grinder — that is why they are quiet — which means anything solid stays in that filter. Rinse it under the tap, get a brush into the mesh. This should be done monthly and almost nobody does it.
The check valve and the pump. Underneath, behind a small cover, there is an impeller. Glass fragments, a fruit label, a pistachio shell. Turn it by hand and make sure it spins.
The drain hose and the high loop. The hose must rise to at least 20 inches under the counter before falling to the drain. Without that high loop the machine siphons and sink water backs into the tub. This is an installation fault we find constantly in Boston kitchens, where the dishwasher was retrofitted into a cabinet run by whoever was cheapest and the hose was simply run flat to the trap.
The air gap or the disposal knockout. If there is an air gap on the counter, take its cap off and clean it. And if a garbage disposal was fitted after the dishwasher, check the knockout plug was actually removed — a brand-new disposal with the plug still in place is a dishwasher that has never drained since, and we find this more often than you would think.
E15: the leak sensor tripped
E15 means the base pan float has risen and the machine has gone into flood protection — usually with the drain pump running continuously, which is the giveaway sound.
Sometimes there is a genuine leak: a door seal, a hose clamp, a spray arm seal, a cracked sump. Sometimes it is over-sudsing that filled the base pan with foam, which happens when somebody used washing-up liquid, or far too much detergent for the water.
The recovery: turn it off at the breaker, tip the machine back onto its rear feet — carefully, with a towel down — for a few minutes to let the pan drain, and set it back down. If E15 stays away, it was suds or a one-off spill. If it returns, there is a real leak and it needs finding, because that float exists specifically to stop your floor being ruined.
Soft water and the detergent problem
Greater Boston runs on MWRA supply off the Quabbin and Wachusett; Cambridge draws from Fresh Pond. Both are naturally soft, roughly one to two grains.
Almost every dishwasher detergent dose is written for considerably harder water. In soft water the excess has nothing to bind to, so it foams, it deposits a white film on glassware that everybody mistakes for limescale, and it contributes directly to the E15 sudsing above.
Bosch machines with a water-softener compartment should be set to the softest setting for this supply — a machine set for hard water in soft water will over-regenerate and make the film worse. If you are using tablets, half a tablet genuinely does the job here on most loads.
The exception, as always, is the well-supplied edge of our footprint — Wellesley, Dover, Canton, Westwood, Dedham, Needham — and Essex County, none of which is on the MWRA system. There the standard dose is appropriate and the softener setting should reflect it.
The other faults, briefly
Not filling. Inlet valve, or the aqua-stop assembly on models fitted with one. The aqua-stop is a solenoid valve at the tap end and it fails as a unit.
Not heating. Bosch uses a flow-through heater integrated with the circulation pump on most models, so a heating failure is often a pump assembly rather than a discrete element. Worth knowing before you are quoted.
Door will not latch, or falls open. Spring and cable assembly on the hinges. The cables fray and snap, and it is a modest repair.
Worth doing before you call
Run the filter clean, check the rinse aid, confirm the drain hose has a high loop, and note the exact code as displayed. With those four things and the model number — inside the door on the right edge — there is a good chance we arrive with the right part rather than to look at it.