A Bosch SHP78CM5N that leaves dishes dirty, with food on the top rack or a gritty film on glasses, has a cleaning problem with a short list of causes, and almost all of them sit in the wash path rather than the electronics. This 800 Series model has a third rack, a quiet 42 dBA motor and CrystalDry drying, and its wash is thorough when water reaches every dish and the pump is not starved. The first suspect is the manual filter at the tub floor.
The checks in more detail
Bosch dishwashers have no disposer to chew food, so the filter collects it, and a filter packed with debris restricts the flow of wash water, so the arms spray weakly and the pump labours. Twist out the cylinder filter and the flat micro-filter beneath it, rinse them under the tap with a soft brush and check the sump for a label, a bone or broken glass; then lock them back in properly, since a filter that is not seated lets debris recirculate. Next look at the spray arms.
Lift the lower arm and the middle arm and check that each spins freely and that the nozzles are not blocked by seeds, grit or limescale; clear the holes with a toothpick. Check that the third rack and tall items are not blocking an arm or the water feed to it. Load plates facing the center with space between them, and do not nest bowls. Then water and detergent. Run the tap until it is hot before starting, since the wash heats only so far.
Use fresh detergent in the right amount, because old tablets can fail to dissolve; powder and gel work better in a short cycle. Use rinse aid to stop spotting, and in hard water add dishwasher salt if your machine has a softener. If dishes are still dirty with a clean filter, free arms and hot water, run a cleaning cycle with a dishwasher cleaner and note whether an E code appears; a pump or heater fault needs a technician with the FD number from the door plate.
Differential
Likely causes of “Bosch 800 Series SHP78CM5N dishwasher does not clean dishes”, and how to tell them apart
- 1
A clogged filter
What separates it Food in the sump and a weak spray
How to confirm Clean both filters
- 2
A blocked spray arm
What separates it Part of the load stays dirty
How to confirm Clear the nozzles and check it spins
- 3
Items blocking the arms
What separates it Dishes in one area are always dirty
How to confirm Reload with space
- 4
Cold incoming water or old detergent
What separates it A film and cold-tasting wash
How to confirm Run the tap hot first and use fresh detergent
- 5
Limescale in hard water
What separates it A cloudy film
How to confirm Use salt and a cleaner
Before you touch a setting
Record this first — changing settings destroys the evidence
- Whether the filters were cleaned and when
- Which rack stays dirty
- Whether the arms spin freely
- Any E code shown
Try in this order
0 of 6 completedClean the filters
ReversibleCylinder and micro-filter.
Check the spray arms
ReversibleThey must spin and be clear.
Reload
ReversiblePlates facing the center.
Run the tap hot
ReversibleBefore starting.
Use fresh detergent
ReversibleAnd rinse aid.
Run a cleaning cycle
ReversibleIf dishes stay dirty.
Model-specific
What is true of this model and not of its siblings
- The manual filter
- Bosch has no disposer, so the filter is the only thing between food and the pump. Cleaning it monthly keeps the wash strong.
- Spray arms
- Each arm must spin freely. A nozzle blocked by limescale or a seed leaves a dead zone on the rack.
- Third rack
- RackMatic lets it move for tall items, but check that nothing blocks the middle arm below it.
- Hot water
- Running the tap hot first gives the wash a warm start; a cold start leaves a film.
- Detergent
- Fresh tablets dissolve properly; old ones leave residue.
- Bosch help
- Quote the model and the FD number from the door plate.
Stop boundary
When this stops being a self-service repair
- !Do not run the machine with broken glass in the sump
- !Switch off before reaching into the base
- !Call Bosch if an E code returns with a clean filter
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Why are my Bosch dishes dirty?+
Usually a clogged filter or a blocked arm.
Do I need to pre-rinse?+
Scrape but do not rinse; the sensors need some soil.
Is the third rack a problem?+
Only if tall items block the middle arm.
Does hard water matter?+
Yes, it causes a film; use salt and a cleaner.
Does CrystalDry affect cleaning?+
No, it only affects drying.
When do I call a technician?+
If an E code appears with clean filters and free arms.