Multi-Split, One Bedroom Warm: Seized Expansion Valve
One bedroom on a multi-split stays warm and the rest are unaffected. Whether that is a leak, a failed unit, or something smaller.
By Team Snowflake | Updated 24 Aug 2026
How this presents
One bedroom cooling weakly while the other rooms on the same system hold temperature without difficulty. The affected unit runs, its fan is normal and its filter is clean. Air from it is mildly cool rather than cold.
- Setup
- Toshiba Multi-split4-6 yearsCondoBukit Timah
- Misread as
- A leak affecting only one room, or an indoor unit that has failed and needs replacing.
- Check first
- Temperature difference across the affected coil compared against a working room
What else produces this
Everything shared is eliminated by the rooms that work, which leaves whatever belongs to the failing room alone. Its coil is clean and its airflow is fine, so what remains is how much refrigerant reaches it. That is decided by its own metering valve rather than by the system charge. The pipes at that unit will show it, because a coil receiving too little runs less cold than it should and the temperature difference across it falls well short of what the working rooms produce.
Other rooms holding temperature confirm that the shared refrigerant and the machine outside are both sound.
A clean coil and normal fan remove airflow and fouling from the affected room's explanation.
A small temperature difference across the affected coil shows too little refrigerant reaching it.
Its own metering valve failing to open fully accounts for that without any loss from the system.
Why it happens
On a shared installation every indoor unit meters its own refrigerant through a valve that opens and closes to match what the room is asking for. Deposit, moisture or an electrical fault in the drive can leave it part-closed. The room behind it then receives a fraction of what it needs, while every other room continues to be served normally, because nothing they depend on has changed at all.
What resolution involves
The affected unit's valve is repaired or replaced and that room recovers, with the rest of the system untouched throughout. The reasoning is what carries over. On a shared system, an isolated symptom points at whatever belongs to that room alone, and the flow-control valve is the item most people do not know exists.
How to tell it worked
Temperature difference across the coil in the failing room, set beside the same measurement in a room that works. Two similar figures mean the metering is right; a smaller one means the valve is still short.
Before you approve a quote
Every room meters its own refrigerant
- A shared charge does not mean shared delivery. Each unit controls what reaches its own coil.
- An isolated symptom on a shared system belongs to that room: its coil, its branch, or its metering valve.
- Compare the temperature difference across coils between rooms. The working room is your reference.
Questions this case answers
Can one bedroom go warm on a multi-split when the pressure is fine?
How do I know another gas top-up will not fix it?
What happens if one room's valve seizes and the rest are fine?
Can the repair be kept to one room?
Ready to get started?
Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.