The short answer
A Bosch B-series freezer that runs but will not hold temperature is nearly always an airflow problem rather than a failed compressor. A freezer holds food safely at 0 F (-18 C) or below, so the first job is to establish whether the cabinet is actually above that or only feels wrong.
What you observe
- Ice cream soft while everything else seems frozen — The most sensitive item reports the problem first, long before anything thaws.
- A sheet of frost on the back wall of the cabinet — Not the usual dusting. A sheet means the defrost cycle is not clearing it.
- The unit runs continuously and never seems to stop — Working hard and never getting there, which is the same fault seen from outside.
- One part of the cabinet warmer than the rest — Air is not being distributed, which points at the fan or at what is blocking the vents.
- Condensation or ice around the door edge — Warm room air getting in, which is a seal question.
- NEAR MISS - the cabinet is silent and nothing is cold at all — That is a no-power or start-relay fault rather than a cooling one, and it is diagnosed from the supply end instead.
Likeliest causes here
- The door not sealing — A gasket that has hardened, a hinge that has dropped or a drawer holding the door a fraction open lets warm, wet air in continuously. First, because on these models a door in a tight surround is the easiest thing here to get slightly wrong.
- The condenser airway blocked — The coil has to dump heat into the room, and a coil breathing through dust or a blocked grille cannot. Second on these models: this installation breathes through a grille in the cabinetry, which is easy to obstruct and easy to forget.
- The return and supply vents blocked by contents — A cabinet packed to its back wall stops the cold air circulating, and the thermostat then reads a place the air never reaches. Third on this family - free to test by unloading the back of the cabinet.
- The evaporator fan not running — The fan behind the rear panel moves the cold air; without it the evaporator gets very cold and the cabinet does not. It comes last here - listen at the open door with the switch held, which is the whole test.
- Where this ranking departs from the brand-generic page — The cause that moves is the door not sealing. It leads on this family because the cabinet is built in flush and breathes through a grille in the cabinetry. That is a property of the platform rather than of the brand, which is why the page above this one cannot rank it the same way.
Check in this order
- Close the door on a sheet of paper at several heights — It should grip the same everywhere. Check no drawer or package is holding the door a fraction open. It leads on these models because the construction puts it within reach before anything else on the list.
- Clear the ventilation grille and vacuum the coil area — The heat has to go somewhere; a blocked airway is the commonest reason it does not.
- Unload the back of the cabinet and find the vents — Nothing should sit against them. A packed cabinet starves its own circulation.
- Listen at the open door with the door switch held in — Silence where the fan should run explains a very cold evaporator and a warm cabinet.
Before you open anything
Safety
Unplug the appliance or switch off its breaker before removing any panel - a capacitor can hold a charge after the power is off. Never chip ice off an evaporator with a knife or a screwdriver: the tubing behind it is thin, and a puncture turns a defrost fault into a sealed-system replacement. Refrigerant work is licensed work and is not an owner job under any circumstances.
When to call
The seal, the load, the vents, the grille and the control setting are owner ground on these models, and together they explain most warm-cabinet calls. Call once those are clean and the cabinet still will not hold: what remains is the defrost circuit, the evaporator fan and the sealed system, all of them behind panels. Call sooner on a built-in column, because the parts that remain are behind a cabinet that has to be released from its surround before anything can be reached.
Nearest pages
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
