**Technical Analysis of Hisense Air Conditioner; Inverter Air Conditioner, Outdoor Unit Has No Output Voltage After Running for a While**
**Model:** KFR-50LW/BP
**Fault Phenomenon:** The outdoor unit stops immediately after starting, and after running for a while, there is no output voltage from the outdoor unit.
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**Repair Process:**
Firstly, we conducted a routine analysis. When the outdoor unit stops immediately after starting, this fault generally occurs in two areas:
1. Faults caused by the compressor, including issues with the phase sequence of U, V, W. If the phase sequence is incorrect, it may also cause the fault where the unit stops immediately after starting.
2. Faults in the wiring harness, including the +15V power wiring harness and the signal wiring harness. There are two sets of wiring harnesses, and if there is poor contact, the above situation may occur.
It is important to distinguish between the fault phenomenon described here and a short circuit in the subsequent stage during analysis.
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**Repair Measures:**
After analyzing the aforementioned causes and taking appropriate actions, the fault still persisted without significant improvement. Then, we shifted our thinking and conducted further analysis. Since the unit could start momentarily, we suspected that there might be an issue with the power supply circuit of the outdoor unit. If the outdoor unit loses +12V instantly, the power on the outdoor unit's power board will not reach the outdoor unit, resulting in no power supply to the outdoor unit.
There are three factors affecting the power supply to the outdoor unit: one is the +12V power supply, another is the PTC, and the third is the relay. Through testing and replacing components, it was determined that the poor contact of the +12V wiring supplying power to the outdoor unit relay was the cause of the problem.
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**Conclusion:**
Soft faults can occur anywhere, so when analyzing the occurrence points of soft faults, we must consider all aspects comprehensively. Some components cannot be measured superficially; they must also be tested under actual operating conditions. Only in this way can soft faults be judged more accurately. Additionally, it should be noted that the fault reporting of this machine is not obvious. The form of fault reporting is as follows: a fault is reported immediately after startup, and then the machine enters normal operation.
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**Source of Article:**
http://blog.sina.com.cn/haixinkt119