220-1101 Question 279
Single answerFan considerationsA technician is upgrading a small-form-factor desktop that has been shutting down unexpectedly during long video-rendering jobs. The technician finds that the original rear case fan has failed and must be replaced. Space inside the case is limited, and the motherboard has a 4-pin system-fan header available. Which replacement fan should the technician choose FIRST to best maintain proper cooling and fan control in this system?
- A
A 120 mm 4-pin PWM fan that matches the case mounting points and airflow direction requirements
- B
A 140 mm 3-pin DC fan because larger fans always provide better cooling regardless of case size
- C
A high-RPM 2-pin fan spliced directly to the power supply, bypassing the motherboard header
- D
Any fan that physically spins, as fan size and connector type do not affect system operation
Show answer and explanation
Correct answer: A
Explanation
When replacing a failed fan, the technician should verify several practical factors: physical dimensions, mounting-hole alignment, connector type, airflow direction, and whether the motherboard can monitor and control the fan. In A+ Core 1 contexts, fan considerations commonly include proper airflow through the case, matching fan size to available space, and understanding 3-pin versus 4-pin fan connections. A 4-pin PWM fan on a 4-pin header is generally the best match because it supports motherboard-controlled cooling behavior and monitoring. Best practices from PC hardware manufacturers and motherboard documentation emphasize using compatible fan sizes and connectors, maintaining intended front-to-back or bottom-to-top airflow patterns, and avoiding ad hoc wiring choices when a proper supported replacement is available.
- A. Correct.
Correct. The best first choice is a replacement fan that fits the chassis and mounting points, supports the available 4-pin motherboard header, and provides the intended airflow path. A 4-pin PWM fan allows the motherboard to monitor and control fan speed more precisely, which is especially useful in a small-form-factor system where heat buildup and noise control matter. Matching physical size and airflow direction is critical because an incompatible fan can block airflow or fail to install properly.
- B. Incorrect.
Incorrect. A 140 mm fan may move substantial air, but it is not automatically better, especially in a small-form-factor chassis with limited space and fixed mounting points. Larger fans cannot be assumed to fit. Also, a 3-pin DC fan may work on some 4-pin headers, but it may offer less precise control depending on the motherboard implementation. The misconception is that bigger is always better; in practice, fit, header compatibility, and airflow design come first.
- C. Incorrect.
Incorrect. Powering a fan directly from the power supply can make it run, but bypassing the motherboard removes normal speed monitoring and control, which can increase noise and reduce the system's ability to respond to temperature changes. A 2-pin fan also lacks the tachometer and PWM control features commonly used in modern desktops. This is a plausible workaround in some situations, but it is not the best first choice for a proper repair.
- D. Incorrect.
Incorrect. Fan size, connector type, and airflow direction all matter. A physically spinning fan that does not fit the mounting holes, does not connect properly, or pushes air the wrong way may fail to cool the system effectively. This option reflects a common misconception that any replacement fan is acceptable as long as it turns on.