CR104B Vehicle Electrical and Mechanical Systems Practice Test 2026 – All-in-One Guide to Master Your Exam Preparation!

Relays are used in power window systems to let a small, low-current control circuit operate a high-current motor safely. The window motor needs a fairly large amount of current, especially at startup, which would stress a normal control switch or driver if it had to carry it directly. The relay’s coil is energized by the control circuit with only a small current; that coil then closes heavy-duty contacts that supply the motor with the higher current it needs. This arrangement protects the control electronics from the motor’s current demands and voltage spikes, and also reduces wear on the cockpit switch by keeping the high current out of the control path. Weather sealing or noise reduction isn’t the primary purpose of the relay in this context.