As the capacitor ages, its capacitance decreases while its equivalent series resistance (ESR) increases. When this happens, the capacitors no longer adequately serve their purpose of filtering the direct current voltages on the motherboard, and system instability results. Some common symptoms are:
- Not turning on all the time; having to hit reset or try turning the computer on again
- Instabilities (hangs, BSODs, kernel panics, etc.), especially when symptoms get progressively more frequent over time
- CPU core voltage or other system voltages fluctuating or going out of range, possibly with an increase in CPU temperature as the core voltage rises
- Memory errors, especially ones that get more frequent with time
- Spontaneous reboots
- In case of on-board video cards, unstable image in some video modes
- Failing to complete the POST, or rebooting before it is completed
- Never starting the POST; fans spin but the system appears dead
Unlike the physical signs which are conclusive evidence the capacitors are failing, many of the operational signs may be caused by other factors, such as a failing power supply, dust clogging a fan, bad RAM, or other hardware problems. Instability, once the operating system has loaded, may indicate a software problem (such as some types of malware, poorly-written device drivers or software), and not a hardware problem at all. If any of these symptoms are experienced, removing the system's case and inspecting the capacitors, especially those around the CPU, may immediately identify capacitors as the cause. If there are no physical signs, an oscilloscope may be used to examine the voltage on the capacitors, with excessive ripple voltage being a sign the capacitors are not doing their job.
