The short answer
A Bosch KGN refrigerator that is warm in one compartment and cold in the other has an airflow fault, not a refrigeration fault. On the two models below the two compartments share one cold source, so a blocked path or an evaporator that has iced over starves one side while the other stays fine. The sealed system is the last thing to suspect, not the first.
What you observe on these models
- It cools, then warms, then cools again over days — Cycling behaviour points at defrost, a sensor, or a door that is not always closing.
- The back of the cabinet is hot to the hand — Normal in itself, but a condenser packed with dust makes it hotter and less effective.
- There is no airflow felt at the fresh-food vents — Hold a hand at the vent with the door open and the fan running; nothing there is the finding.
- The door does not pull itself shut the last inch — A seal or a levelling problem, and it warms the cabinet without any component failing.
- NEAR MISS - warm with water on the floor — Water changes the picture: start on the leak page for the KGN family instead.
Causes, most likely first on the KGN family
- Defrost failure — First on the two models below where the freezer rear wall carries a sheet of frost. Defrost runs on a schedule, and when it stops the ice closes the air path over days. Everything else on this page then follows from it.
- Circulation: fan, vents and how the cabinet is packed — Second. A box against the rear vent does what a failed fan does, and it is free to fix.
- Seals, hinges and doors left ajar — Third. Continuous warm-air ingress overloads the cabinet, and a drawer that holds a door open a fraction is easy to miss.
- Condenser and the sealed system — Last. Dust on the condenser is yours to clear; anything past it is measurement work and licensed work.
Check in this order, and why
- First: rule out the free causes — Doors closing fully, nothing packed against the rear vents, the unit not boxed in, and the condenser clear of dust.
- Second: compare the compartments — Cold freezer plus warm fresh food is airflow; both warm together is defrost, ingress or the sealed system. This splits the diagnosis on the two models below.
- Third: give any change a full day — Cabinets recover slowly. Judging a change after an hour produces a wrong conclusion and a second call.
- Fourth: measure again before calling — Numbers from a thermometer, taken twice, are what a technician works from. Say what it reads rather than that it feels warm.
Before you open anything
Safety
Isolate the appliance before any panel comes off, and treat the sealed system as out of bounds: refrigerant work is licensed work and the tools for it are not owner tools. A capacitor can hold a charge after the power is off. If food has been above 40 F (4 C) for hours, deal with the food before dealing with the appliance.
Models in the KGN family
Reference| Model number | Family key |
|---|---|
| KGN36IJ3AA | bosch:refrigerator:kgn |
| KGN36VI3AA | bosch:refrigerator:kgn |
When to call a technician
Call once the seals, the vents, the condenser and the packing are all clear and a measured compartment is still above what food safety needs. On the KGN family defrost components and fans sit behind a rear panel, and the sealed system is licensed work. Call immediately if the unit is silent and warm, because that is power or compressor rather than airflow.
Sources — The symptom-report corpus recorded against Bosch KGN refrigerator pages for this fault is cited below. No share is quoted from it anywhere on this page: the snapshot reaches this page as a provenance chain without values, so every ordering here is technician judgement rather than a measured proportion.
Documented- amazon-reviews — amazon-reviews, fetched 2026-09-02
Other faults covered for the KGN family
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
