If your Mitsubishi City Multi system is showing error code 1102, the refrigerant leaving your compressor got too hot and the system shut down.
Of the protection codes on a VRF system, this is one of the ones we take most seriously. Discharge temperature protection exists to stop a compressor destroying itself, and by the time it trips, the compressor has already been working in conditions it was not designed for.
What this means for your building
Refrigerant leaving the compressor is the hottest point in the circuit. The system monitors that temperature closely, because it is the clearest early indicator that the compressor is in trouble.
When it exceeds the safe threshold, the system stops.
The critical thing to understand: 1102 is almost always a consequence of something else. High discharge temperature is what happens when the compressor is starved of refrigerant, cannot reject heat, or is being asked to work outside its envelope. The code tells you the compressor is suffering. It does not tell you why.
The preliminary code
1202 is the preliminary code for 1102 — raised when high discharge temperature is detected but not yet confirmed.
A 1202 in your fault history is the system telling you this was developing before it became a shutdown. That is the moment when the underlying cause is usually cheap to fix, and it is almost always missed because nothing visibly stopped working.
If you have access to your fault history, it is worth checking for preliminary codes even when nothing is currently wrong.
How urgent is it?
Urgent. More so than the codes that simply stop a zone from conditioning.
Compressor oil breaks down at sustained high temperature. Once lubrication degrades, wear becomes mechanical and permanent, and no amount of later correction reverses it. Each restart without addressing the cause repeats that exposure.
There is no safety hazard here. The risk is entirely to your most expensive component.
What it typically costs
Medium to high, driven almost entirely by what is causing it.
If the cause is a low refrigerant charge from a leak, you are looking at leak detection and recharge. If it is a failed expansion valve, that is a moderate component repair. If it is restricted airflow or a dirty coil, considerably less.
The expensive outcome is the one where 1102 was reset repeatedly: compressor replacement, which is the highest-cost repair on a VRF system.
The economics here are stark. Nearly every cause of 1102 is cheaper than the compressor it threatens.
What causes it
- Low refrigerant charge — refrigerant cools the compressor, so a leak makes it run hot. This is why 1102 and 1301 so often appear together.
- Failed or stuck expansion valve — not metering correctly, so insufficient cool refrigerant returns to the compressor
- Restricted refrigerant flow — blocked filters or driers
- Poor heat rejection — dirty outdoor coil or failing fan, which raises the whole system’s operating temperature
- Faulty discharge temperature sensor — the least expensive outcome, and worth ruling out
- Compressor already degrading — a compressor with internal wear runs hotter than a healthy one
That last one matters: sometimes 1102 is not the cause of compressor trouble but the first visible sign of it.
What happens if you leave it
This is the code where “just reset it and see” is most expensive.
Sustained high discharge temperature degrades the oil that keeps the compressor alive. That degradation is cumulative and irreversible. A system that trips 1102 repeatedly through a summer is a compressor being consumed.
The pattern we see: a small leak causes low charge, low charge causes high discharge temperature, the code is reset each time, and eighteen months later the compressor fails. The original repair was a leak. The final repair is the most expensive component on the system.
What we check
- Verify the discharge temperature sensor before assuming the reading is real.
- Assess refrigerant charge — low charge is the most common driver.
- Check for leaks if charge is low, rather than simply topping up.
- Test expansion valve operation across the affected circuit.
- Inspect the outdoor coil and fan — poor heat rejection raises everything downstream.
- Review fault history for preliminary 1202 events to establish how long this has been developing.
- Assess compressor condition — because sometimes this code is the symptom of a compressor already in decline.
What you can tell us before we arrive
- Has refrigerant ever been added? Prior top-ups strongly suggest a leak, which is the most common root cause here.
- How many times has it tripped? And roughly over what period.
- Are other codes appearing? Particularly 1301 or 1302 — they often point at the actual cause.
- Has cooling capacity been dropping? Gradual loss of performance often precedes this code.
Related codes
- 1301 — Low pressure fault. Frequently the underlying cause. Low charge raises discharge temperature.
- 1302 — High pressure fault. Shares several root causes around heat rejection.
- 5101–5116 — Temperature sensor faults. If the sensor itself is suspect.
Get the cause found before the compressor pays for it
We are certified on Mitsubishi, Daikin and LG VRF platforms, and we service systems we did not install.
Next business day service for commercial VRF.
Related codes
Error 1301 means low-side pressure dropped below its safe limit. On commercial VRF this often points to a refrigerant leak — the expensive scenario.
Error 1302 means refrigerant pressure exceeded its safe limit and the system shut down to protect the compressor. Left unresolved, it damages equipment.
The 51xx codes are temperature sensor faults. Each number identifies a specific thermistor — cheap parts, but the labour to reach them varies enormously.
Frequently asked questions
What does error code 1102 mean on a Mitsubishi City Multi system?
The temperature of refrigerant leaving the compressor rose beyond its safe limit, and the system stopped to protect itself. It is a protection response. Something is making the compressor work harder or run hotter than it was designed to.
What is the difference between 1102 and 1202?
They are the same fault at different stages. 1202 is the preliminary code, raised when high discharge temperature is detected but not yet confirmed. 1102 is the definite code once the condition is established. A 1202 in your history is an early warning worth acting on.
Is a 1102 error serious?
Yes. Discharge temperature protection exists specifically to prevent the compressor destroying itself. Sustained high discharge temperature breaks down the oil that lubricates the compressor, and once lubrication degrades the resulting wear is mechanical and permanent. No later repair reverses it, which is why repeated resets are costly.
Can low refrigerant cause a 1102 error?
It is one of the most common causes. Refrigerant cools the compressor as it passes through, so a system low on charge runs hotter. This is why 1102 often appears alongside low pressure faults, and why a leak left unrepaired eventually threatens the compressor.
Can a faulty expansion valve cause high discharge temperature?
Yes. If an expansion valve is not metering refrigerant correctly, the compressor can end up with insufficient cool refrigerant returning to it. The valve itself is a far cheaper repair than the compressor it can damage if left unaddressed.
Why does 1102 sometimes appear with other codes?
Because high discharge temperature is usually a consequence rather than a root cause. Low charge, restricted airflow, or a failing expansion valve all raise discharge temperature. The other codes present alongside it often point more directly at the underlying problem.