To keep the power supply cool. If there were no fan the power supply would overheat and fail.
Power supplies don't fail. Idiot.
There are too many possible causes of failure to comment on them here without further information not provided in your question. There can be hundreds of different components in a computer power supply, each of which fail for different reasons and produce different symptoms in the power supply. Ultimately all electronics fails due to "old age" (just like people).
Bond it to a standard regulation fail-proof always-running generator.
When a power supply is overloaded, it can overheat and potentially fail. This can lead to damage to the connected devices, such as a short circuit or a power surge, which can result in data loss or hardware damage. It is important to ensure that the power supply is rated to handle the load requirements of all connected devices to prevent overloading.
A machine that is broken and doesn't perform its intended functions would fail to do work. This could be due to mechanical issues, lack of power supply, or other operational failures.
Personally, I wouldn't use less than a 300 Watt power supply in that situation. But then, I never use less than a 500 Watt power supply when replacing a power supply or building a computer. The advantage is, the larger power supply can easily handle the load and will not run as hot. Since electronic components typically fail more rapidly when they get hot, the larger power supply will usually last much longer. But that's just a suggestion.
Not usually. Any electrical part can go bad though. Usually if electronics are going to fail it is within the first 24 hours or so. The only time I had to change a power supply is because I wanted more power.
the computer will not switch on. May be the SMPS fail leading to a huge spark.
Computer power supplies today do not need daily maintenance. They do need a free air flow to circulate through the power supply to prevent overheating. If there is a filter to prevent dust fro getting in to the power supply, it should be kept clean so that air flow is not restricted. If parts of the power supply get too hot they may fail to function properly or they may burn out.
Yes, you can use a 16V 4.5A power supply for a device that requires 16V 1.5A. The device will only draw the current it needs, so having a higher amperage rating on the power supply is not a problem. Just ensure the voltage matches and polarity is correct.
the most likely cause of that would be the power steering pump failing.